 Subjects -> METEOROLOGY (Total: 106 journals)
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- Long-term spatio-temporal analysis and trends of precipitation over
semi-arid region of Rajasthan-
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Abstract: Abstract Assessing the spatial and temporal variability of climate data is one of the basic requirements for solving water and water management problems. This study performed a comprehensive data quality test, a precipitation concentration index (PCI), Sen’s slope, Mann–Kendall (MK) trend test, and an analysis of the symptoms of drought using rainfall anomaly index (RAI) and standardized precipitation index (SPI). The standard homogeneity test (SNHT), Pettitt test, Buishand range test, and von Neumann scale were used for homogeneity analysis, and most tehsils (administrative boundary) showed the same weather character. PCI annual estimates show high local and temporary variability or irregularity in rainfall distribution. MK tests showed a marked increase in the tendency to high temperatures; however, the trend of annual and extreme rain events was not significant for most of the stations. The extreme dry conditions in 101 years (IMD) were found at Sujangarh. Analysis of size statistics and the trend of rainfall anomaly indices and spatial variability of climate data are important in the integration of water resource planning and management decisions. Rajasthan is an agricultural state in India, the monsoon rainfall largely controls the production of crops, and the proper implementation of regional agro-water management and rainwater harvesting can contribute significantly to agricultural potential. This study paves the way for further exploration of inter-regional hydrological modeling to sustain livelihoods. The mean yearly precipitation has shown a minimal non-significant positive pattern over the dryland ecosystem. Amazingly, 3 year running average has shown a cyclic example of mean yearly precipitation under the changing climatic conditions and in dry and wet conditions at different time scales. The western, northern, and southern parts of the dryland ecosystem have encountered wetter conditions (significant at 95% certainty level), while north-eastern, eastern, and south-eastern regions have seen expanded drier circumstances. Overall, most of the areas are suffering from hyperarid conditions, which needs extreme water management for a below normal-to-normal arid cropping.
PubDate: 2023-09-28
- Trivariate risk analysis of meteorological drought in Iran under climate
change scenarios-
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Abstract: Abstract The aim of this study is to analyze the trivariate risk of meteorological drought using copula functions under climate change scenarios in Iran. For this purpose, SPI-12 is calculated for the historical and future periods and the drought characteristics [severity (S)–duration (D) and magnitude (M)] are extracted and the trend analysis of drought characteristics is performed using Mann–Kendall trend test. Then, trivariate risk analysis of drought variables is performed for historical and future periods. The results of the trend test indicate that the precipitation trend decreased mostly in the northwest and west regions of Iran, while these changes in the future period will be observed in the central regions. According to the results, no significant trend in precipitation and drought characteristics will be observed in the future compared to the historical period. Trivariate risk analysis for the given values of (D = 6, S > 40, M = 2) and (D = 12, S > 40, M = 2) shows that for the given values of severity and duration, increasing duration from D = 6 to D = 12 months, decreases the probability of drought occurrence and return period. Therefore, the conditional risk will increase in Iran under future climate change scenarios.
PubDate: 2023-09-25
- Future photovoltaic solar power resources in Zambia: a CORDEX-CORE
multi-model synthesis-
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Abstract: Abstract The exploration of renewable energy such as wind and solar radiation has the potential of reducing reliance on fossil fuels, thus cutting emissions of carbon dioxide, particulate matter, and several other greenhouse gasses. However, recent findings indicate that wind speed across Zambia is very slow, it is increasing but remains unlikely to support large commercial wind farms. In this study, we explore the future impacts of climate change on solar photovoltaic resources. To do this, we examine the new high-resolution (25 km) Coordinated Regional Climate Downscaling Experiment—CORDEX-CORE simulations for the African domain, using two different emission scenarios until 2100. At an annual scale, results indicate a weak but steady decrease in PVRes of around 0.02 W/m2 per annum under RCP2.6 and about 0.005 W/m2 per annum under RCP8.5. Results further show that at an average of ~ 237 ± 3.3 W/m2 and 212 ± 2.5 W/m2, respectively, RCP2.6 comes along with 12 ± 3% more PVRes than RCP8.5. Thus RCP2.6, a greener and climate-friendly pathway, points towards a higher renewable energy potential across Zambia compared to the business-as-usual pathway.
PubDate: 2023-09-23
- Role of ocean–atmosphere interactions on contrasting characteristics of
two cyclones over the Arabian Sea-
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Abstract: Abstract The role of ocean–atmosphere interaction in modulating the track and intensity of two cyclonic storms, Nisarga and Nanauk, which originated from almost similar locations in June in the Arabian Sea with completely different tracks, is investigated in this study. Sea surface temperature (SST), steering flow, relative vorticity, latent heat flux (LHF), specific humidity, vertical wind shear (VWS), outgoing longwave radiation (OLR), convective available potential energy (CAPE), and Madden–Julian oscillation (MJO) phases are analyzed to elucidate the causes of contrasting characteristics of these two cyclones. During the progression and intensification of the storm Nanauk, SST decreased drastically (magnitude of ~ 4 °C), while VWS anomaly is found to be increased (~ 8 ms−1), followed by entrainment of dry air leading to a decrease in upward LHF anomaly (~ 3.5 to 4 J m−2) hindering further moisture supply. Moreover, just before the storm initiation, the CAPE anomaly was around − 800 to − 1000 J kg–1 and the MJO condition was also unfavorable for the continuous intensification of the cyclone. All these factors contributed to the quick dissipation of cyclone Nanauk. However, high SST (~ 31 °C) along with other favorable atmospheric conditions contrary to cyclone Nanauk provided a conducive environment for Nisarga to intensify and prevail. A high-pressure anticyclonic circulation at the eastern side of Nisarga over Indian land dragged the storm north-eastwards across the Maharashtra coast. The convective phase of MJO (magnitude > 1) along with the strong lower tropospheric westerly wind at the west side of the convective system also helped cyclone Nisarga to propagate eastward.
PubDate: 2023-08-31
- A comparison study between the use of single-point versus areal-mean
rainfall values from a high-resolution model when verified against
satellite retrievals for three typhoons hitting the Philippines-
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Abstract: Abstract In this study, effects of using areal-mean instead of single-point output values from a cloud-resolving model to verify its quantitative precipitation forecasts (QPFs) in terms of the categorical 2 × 2 matrix against satellite rainfall retrievals are assessed for three typhoons that hit the Philippines. The motivation behind this work stemmed from the fact that categorical measures are point-to-point methods but satellite estimates are considered areal-mean values. Overall, we find that using areal-mean values have small but positive impacts on categorical statistics, mainly due to a better overall agreement between satellite-derived rainfall and model outputs after areal averaging with a smoothing effect. These impacts are also statistically significant up to high thresholds of roughly ≥ 350 mm. Using areal means from the model, the threat scores (TSs) improve at low thresholds by about 0.02–0.05, primarily owing to increases in the probability of detection (POD) of observed rainfall events, so the smoothing effect helps convert some misses into hits. In cases with low frequency bias, similar improvements in TSs also occur across middle and even high thresholds (up to 500–750 mm) as both POD and success ratio (SR) rise, with the latter indicative of a lowered false alarm ratio (FAR). Toward the extreme thresholds, results are more mixed and the confidence level of significance drops, but the TSs there are already low (≤ 0.08) against the satellite data regardless of the method adopted.
PubDate: 2023-08-30
- Suitable thermodynamic indices for the prediction of thunderstorm events
for different cities throughout India-
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Abstract: Abstract We have studied the thermodynamic stability indices and their effectiveness in predicting premonsoon thunderstorms for different cities all over India. For that purpose, we have studied 10 thermodynamic stability indices for 24 cities all over India. We have analyzed the upper air radiosonde data at 00 UTC during the premonsoon season of 2016-2018. The mean, standard deviation, and range of variation of the indices have been obtained separately for thundery and nonthundery days. For each of the indices, we have determined the optimum threshold values that give the best prediction skill for each location. Further, we have identified a list of suitable indices that are more effective in predicting thunderstorms for each location. Finally, we have proposed a scheme for premonsoon binary thunderstorm prediction, i.e., whether thunderstorms will occur or not at a particular place, on the basis of optimum consensus among the suitable indices.
PubDate: 2023-08-30
- A simulation study on the recirculation effect of land–sea breeze flows
on atmospheric dispersion of airborne releases in Southeast coast of India
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Abstract: Abstract This study aims to examine the recirculation effect of land and sea breeze flows on atmospheric releases from Chennai and Kalpakkam stations in Southeast coast of India using the WRF and FLEXPART models. High-resolution (2 km) simulations conducted with WRF for 4–6 April 2016 and 13–16 July 2016 showed development of sea breeze circulation under strong land–sea temperature contrast across the coast during daytime. Simulations conducted with FLEXPART in two scenarios of (1) 24 h continuous release, (2) release during sea breeze hours for SO2 from industrial sources at Manali in Chennai and routine low-level Ar-41 from a nuclear power reactor at Kalpakkam stations for 5 April and 14 July indicated considerable differences in SO2/Ar-41 concentrations in the two simulation cases. The simulated plume for 24 h release case showed wide dispersion pattern during flow transition compared to the case in which release is confined to onshore sea breeze hours. The recirculation effect is confirmed from low recirculation factor (0.1–0.3), simulated plume trajectory and particle distributions in the 24 h release case. The simulated SO2 concentrations are about 21 µg/m3 to 2 µg/m3 higher from release location to ~ 20 km in the 24 h release case compared to the release case during sea breeze. Simulated SO2 and Ar-41 concentration/doses at monitor locations during the flow transition period indicated better comparison with monitor data by 24-h release case compared to the release case during sea breeze. Although both simulations underestimated the concentration/dose due to stronger simulated winds, the 24 h release case produced higher concentration/cloud gamma dose by representing the recirculation effect. Overall, simulations suggest that the recirculation effect can lead to increase in the concentration /dose over land by 40% during the wind transition period at the coast.
PubDate: 2023-08-29
- Moisture transport associated with southwest monsoon rainfall over Sri
Lanka in relatively wet and dry rainfall years-
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Abstract: Abstract Atmospheric moisture transport is the most important part of the atmospheric branch of the water cycle, and its anomalies strongly influence rainfall variability. Atmospheric moisture transportation associated with southwest monsoon (SWM) years over Sri Lanka is still not fully understood. Using ERA5 daily data, we investigated the role of moisture transport in relatively wet (SWMWet) and dry (SWMDry) SWM years. Based on composite analysis, seven wet (SWMWet) and nine dry (SWMDry) years were selected from 1985 to 2015. We observe positive (negative) anomalous rainfall in SWMWet (SWMDry) years, while the strong anomalous rainfall is concentrated on the western and southwest parts of Sri Lanka. In SWMWet years, strengthened moisture-laden low-level jets from the Arabian Sea bring excess moisture toward Sri Lanka, while a contrasting pattern is observed in SWMDry years. As a consequence, the climatological mean of net moisture flux (9.46 × 105 kg s−1) over the study domain is increased by 12.37 × 105 kg s−1, resulting in above-average rainfall in SWMWet Years. The results show a decrease in the net moisture flux (5.37 × 105 kg s−1), prescribed below-average rainfall in SWMDry years. The strong relationship (r = 0.63) between net moisture flux and SWM rainfall may explain the observed SWM rainfall variability over the country. Compared to the climatological Vertically Integrated Moisture Flux Convergence (VIMFC, 8.56 × 10−4 kg m−2 s−1), positive anomalous VIMFC (2.63 × 10−4 kg m−2 s−1) in SWMWet years and negative anomalous VIMFC (− 3.70 × 10−5 kg m−2 s−1) in SWMDry years are recorded. These results indicate that the free-tropospheric moisture and moisture flux convergence contributes to strong SWM rainfall by creating environments favorable for producing and maintaining moist absolutely unstable layers. This study helps us understand that the dynamic processes of the atmosphere are more important in regulating the variability of SWM rainfall over the country.
PubDate: 2023-08-28
- Synoptic conditions triggering extreme flood events in Bintan Island in
early January 2021-
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Abstract: Abstract Bintan Island has experienced two consecutive record-breaking rainfall events that took place on 1-2 and 9-10 January 2021, and devastating floods that caused significant losses. This research studied the events to understand the synoptic conditions in which they occurred and to anticipate future incidents. Hourly rainfall data from the Kijang station and Global Satellite Mapping of Precipitation (GSMaP) were used. OLR (outgoing longwave radiation) was also explored as a proxy of convection. Rainfall measurements showed extreme rainfall during both flood events. Anomalies of moisture convergence were observed in the vicinity of Bintan Island during both events. The two extreme rainfall events were the results of interactions among several synoptic phenomena. The first event was associated with strong cold surges and the Borneo Vortex (BV), while the second event involved a moderate cold surge, the Madden-Julian Oscillation (MJO), and the BV. During both extreme rainfall events, the two BV locations were similar and close to Bintan Island, although their initial locations were different. The first BV was formed in the northern South China Sea and then propagated to the equator, due to the southward vorticity advection associated with a strong cold surge, while the second BV stagnated in the west of Borneo. Information on the important factors that triggered extreme events should be useful to manage the coastal environment for future island development.
PubDate: 2023-08-22
- Analysis of the different influence between initial/boundary and physical
perturbation during ensemble forecast of fog-
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Abstract: Abstract To explore the different effects of initial/boundary condition (ICBC) and physical perturbation during fog ensemble forecast, ensemble forecast experiments are done for a heavy fog episode from December 31, 2016 to January 2, 2017. Three ensemble schemes [ICBC, multi-physics (MPY), and a combination of ICBC and MPY (COM)] were compared. Their forecast performances are analyzed in detail and compared with the reference deterministic forecast. The results show that all ensemble schemes, especially the COM, are able to noticeably improve fog prediction. The TS score of ensemble-based fog forecast with 50% probability threshold is higher than that of the control deterministic prediction by ~ 26%. Compared with the ICBC scheme, the MPY scheme can produce a larger ensemble spread and has more skill in fog and the near-surface variables forecast. When ICBC and MPY are combined (the COM scheme), the ensemble spread is enhanced and the prediction performance is also further improved. The sensitivity experiments of different physical parameterization schemes are also analyzed among microphysics, planetary boundary layer, and land surface. The fog forecast is found to be most sensitive to the land surface scheme, followed by planetary boundary layer scheme, and the least sensitive to microphysics.
PubDate: 2023-08-07
- Interactions among Cold Surge, Cross-Equatorial Northerly Surge, and
Borneo Vortex in influencing extreme rainfall during Madden–Julian
oscillation over the Indonesia Maritime Continent-
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Abstract: Abstract The effect of Cold Surge (CS), Cross-Equatorial Northerly Surge (CENS), and Borneo Vortex (BV) on extreme rainfall in the Indonesia Maritime Continent (the IMC) during the wet season (November–March) under active and inactive Madden–Julian Oscillation (MJO) has been evaluated using observational data from 3108 weather stations and gridded GSMaP data. The results showed that the effect of these three phenomena on extreme rainfall in the IMC is significantly modulated by MJO conditions, with the magnitude of the impact varying among regions. The analysis was done by dividing into three groups: single events, double events, and three events. When CS occurs singly, there is an increase in PCE along the CS pathway from the southeastern Philippines when MJO is active and vice versa when MJO is inactive. However, there was an increase in PCE in several other areas in IMC when MJO was inactive. The pattern of PCE increase when CENS is single in active MJO is almost the same as during inactive MJO, namely from Java Island to Nusa Tenggara and along the Indian Ocean in the southern region of Java Island. However, the intensity is higher when the inactive MJO, which suggests that the role of the MJO is to reduce the influence of CENS on extreme rainfall in the area. The effect of BV in the South China Sea on extreme rainfall is higher when inactive MJO than active MJO due to the role of MJO in reducing the frequency of BV events. CS and CENS tend to attenuate their effects on oceanic rainfall extremes mutually. However, they mutually reinforced their influence on the mainland when the inactive MJO. CENS and BV reinforce each other’s influence on each other’s locations when active MJO. However, it’s the other way around when inactive MJO. CS and BV reinforce each other’s influence on extreme rainfall when they occur together, either when the MJO is active or inactive, but CS is more likely to strengthen the development of BV. MJO has the property of weakening the influence of CS + CENS + BV around Java Island and the southern IMC if they occur together.
PubDate: 2023-07-17
DOI: 10.1007/s00703-023-00978-x
- Impacts of CENS and MJO phenomena on diurnal cycle of local convection,
moisture convergence, and rainfall over land, coast, and sea areas in the
western part of Java Island-
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Abstract: Abstract This study aims to investigate the effect of large-scale phenomena, particularly Cross Equatorial Northerly Surge (CENS) and Madden–Julian Oscillation (MJO), on the diurnal cycle of local convection, moisture convergence, and rainfall over the land, coast, and sea in the western part of Java Island. The data used in this study were the CENS and MJO indices, Convective Available Potential Energy (CAPE), convective inhibition (CINH), Vertically Integrated Moisture Flux Convergence (VIMFC), and rainfall from atmospheric reanalysis of the global climate (ERA-5) for 18 years (2001–2018). The average diurnal profiles of CAPE, CINH, VIMFC, and rainfall over five different locations (mountain, coastal land, coast, coastal sea, non-coastal sea) were plotted to see their patterns under five different large-scale conditions: CENS, Active MJO (AMJO), CENS + Active MJO (CAMJO), CENS + Inactive MJO (CIMJO), and the mean condition. The results showed a distinctive and regular character of diurnal profiles of CAPE, CINH, VIMFC, and rainfall in the five locations caused by the specific responses of different underlying surface properties to the diurnal cycle of incoming solar radiation. Furthermore, CENS tended to reduce CAPE (~ 33% reduction, averaged over all locations), which might suppress free (natural) convection. CENS also tended to reduce CINH (~ 41%), which might facilitate convection. Conversely, CENS tended to increase VIMFC significantly (~ 174%), probably through its interaction with the land breezes, which could induce forced convection. As a result, rainfall significantly increased (~ 63%) during CENS. AMJO showed similar effects to CENS but with much weaker influences. On average, AMJO reduced CAPE (~ 14%), slightly reduced CINH (~ 2%), increased VIMFC (~ 28%), and slightly reduced rainfall (~ 3%). However, the effects were the strongest when CENS and AMJO coincided (CAMJO), during which CAPE reduced (~ 37%), CINH reduced (~ 31%), VIMFC increased (~ 334%), and rainfall increased (~ 123%). The effect of CENS and AMJO was strongest over the coastal area, where rainfall increased by ~ 215%. Therefore, one of the most important results from this study was that the increase in rainfall during CENS and AMJO was not caused primarily by the increase of free convection (indicated by the CAPE), which tended to decrease. The increase of rainfall during CENS and AMJO was found mainly due to the increase of moisture convergence (indicated by the VIMFC), which might induce forced convection. We also found that a relatively high value of CINH tended to coincide with a lower value of rainfall, indicating a possible role of CINH in preventing convection. The results of the analysis of the effects of CENS and MJO on the diurnal cycle of CAPE, CINH, and VIMFC have given a better understanding of the detailed mechanisms that produce rainfall increase, which have not been much discussed in previous studies. During CENS/MJO, CAPE decreased, so its role was reducing free convection. CINH also generally decreased, so its role was increasing the potential for convective initiation. VIMFC tended to increase significantly, especially around the coast, so its role was increasing the potential for convection. The role of VIMFC tended to be dominant in increasing rainfall. Conversely, the role of CAPE was less important since it was reduced. The effects of MJO were similar to but weaker than CENS in reducing CAPE, reducing CINH, and increasing VIMFC.
PubDate: 2023-07-13
DOI: 10.1007/s00703-023-00979-w
- Hailstorms over India during the summer season
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Abstract: Abstract Hailstorm activity over India is seasonal and mainly occurs from March to June. The present study analyzes the diurnal spatial pattern of hail event occurrence and its intensity based on the hailstorm data of the India Meteorological Department surface observatories during March to June for the years 2014–2021. The study indicates that in all months, unlike thunderstorm events, hail events were clustered around the afternoon temperature maximum, becoming insignificant in the post evening hours. Spatially in March, hail events were mostly confined to the Himalayas. Their frequency increased in April throughout the Indian region with significant increase over the plains of India. In May, the frequency of hail events gradually decreased in the Himalayas, but persisted over the plains of India, becoming insignificant thereafter throughout the Indian region in June. Small hail events (<1 cm diameter hailstones) preferentially occurred in the Himalayas. Moderate (1–1.9 cm diameter hailstones) to severe hail events (≥2 cm diameter hailstones) were rarer and more uniformly distributed throughout the Himalayas and plains of north and central India. They occurred later in the day as compared to small hail events. The steep decrease in frequency of small hail events beyond April indicates that with the increase in the height of the freezing level as the months progressed, ordinary thunderstorms were less able to form significant hail particles that travelled to the ground without melting, through a progressively warm sub-cloud layer of air. On the other hand, moderate to severe hail events form in tall and deep thunderstorm cells, with significant cloud fraction above the freezing level and strong updraft velocity. Such deep thunderstorm cells occur as a result of strong large scale low to middle tropospheric thermodynamic and dynamic support, are less frequent and peak during afternoon to evening hours. As the season progresses, the warming of the subcloud layer significantly affects the size of hail particles reaching the ground. The warming atmosphere and changing character of the mesoscale convective systems in June subdued most of the hailstorm activity over the Indian region.
PubDate: 2023-07-06
DOI: 10.1007/s00703-023-00980-3
- Temperature and precipitation extremes’ variability in Turkey
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Abstract: Abstract Extreme weather events have become more frequent since the second half of the twentieth century. This study examines the long-term changes in temperature and precipitation extremes in two sequential periods over the period 1960–2019 using daily maximum, minimum, and mean temperatures and total precipitation for the four conventional seasons in Turkey. First, the Probability Density Function (PDF) for the mean temperature and precipitation are analyzed for the sequential periods. Second, extreme and relative value indices of the Expert Team on Climate Change Detection and Indices (ETCCDI) are used to evaluate changes in climate regions of Turkey for the considered period. A general upward trend in temperature indices is seen over the regions, but precipitation indices have more variable outcomes. The monthly minimum value of the daily maximum temperature (TXn) index has a 2 °C decades−1 increase, and except for five stations, there is a 1 °C decades−1 increase between the two sequential periods. While the annual total precipitation (RR ≥ 1 mm) (PRCPTOT) index has increased by 50 mm in the Black Sea, Continental-b and, Continental-c regions it has decreased in Mediterranean, Continental-a, and Transition regions. Similarly, very wet days (RR > 95th percentile) (R95p) and extremely wet days (RR > 99th percentile) (R99p) indices confirmed that the regions have not experienced an increase in extreme precipitation during the second half.
PubDate: 2023-06-28
DOI: 10.1007/s00703-023-00976-z
- Evaluation of WRF-ELEC model to forecast lightning over the North Eastern
region of India-
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Abstract: Abstract In the past few years during the pre-monsoon season, the Weather Research Forecast model coupled with Electricity (WRF-ELEC) has been used to forecast lightning activities over the North Eastern region of India. The model underestimated the events without lightning data assimilation and forecasted only a few cases. Instead, the model capability was significantly improved by assimilating lightning data. It can predict above 91% with a 0.78 success ratio in the lead-time of one hour. The validations have been done for 67 thunderstorm days with 870 cases. We noticed the model capable of forecasting up to 3–4 h with acceptable accuracy, which worsens after increasing the lead-time further. In addition, we found the WRF-ELEC biased to the places of lightning location once severe lightning activities over specific areas. That means the thunderstorm gets steady from the model though moving forward in reality. This study focused on assessing the capability of WRF-ELEC and found that it can forecast specified locations with actionable lead-time. The overall goal of this work is to show the present capability and limitations of using the WRF-ELEC model that may help to effectively operational lightning and rainfall warning.
PubDate: 2023-06-26
DOI: 10.1007/s00703-023-00977-y
- Optimization of solar panel tilt angles using isotropic and anisotropic
models at sun-belt boundary regions-
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Abstract: Abstract It is crucial to make the most efficacious usage of solar radiation, one of the renewable energy sources increasing every day. In order to make practical usage of solar radiation, it is necessary to correctly adjust the solar panel tilt angle that collects solar radiation. Solar panel tilt angles were optimized using isotropic and anisotropic models for the first time in Eskisehir, Turkey. This study applied a mathematical model to identify the ideal tilt angles for solar panels. A combination of selected anisotropic and isotropic models was used in the calculations. The Turkish State Meteorological Service’s archived data were used. The optimal tilt angles for monthly, seasonal, and annual solar panels were established. It has been discovered that the annual optimum solar panel tilt angle should be set to 33° in the isotropic model, whereas in the anisotropic model, to 35°. It was found that the anisotropic model approach is more advantageous than the isotropic approach in collecting solar radiation at a fixed optimum tilt angle. These findings may serve as examples for locations at different coordinates at the same latitude.
PubDate: 2023-06-18
DOI: 10.1007/s00703-023-00975-0
- The anomalous weather parameters that lead to the extreme rainfall of
Kerala in August 2018-
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Abstract: Abstract Extremely heavy rainfall occurred over Kerala, southwest coast of India, during mid-August 2018 resulting in devastating floods. This flood may be called “the flood of the century” as the state has not experienced a flood of this magnitude since the 1924 flood. The rainfall over Kerala during June, July and August 2018 was 15%, 18% and 164% above normal. To examine the reasons for this anomalous phenomenon, the meteorological conditions during this period are studied by analysing different parameters, such as wind, rainfall, potential evaporation, latent heat, outgoing longwave radiation, etc., and it is found that a combination of several rain favouring conditions prevailed at that time. The positive phase of Madden–Julian Oscillation (MJO) coupled with a monsoon depression in the Bay of Bengal and a weak trough in the south-eastern Arabian Sea strengthened the monsoon Low-Level Jet (LLJ) bringing moisture-laden winds over Kerala. The rising limb of Walker and Hadley circulations was also found over Kerala, which gave favourable updraft for cloud formation. In addition, the core of the Tropical Easterly Jet (TEJ) was found over the Kerala and Karnataka region. The cyclonic circulation in the mid-troposphere observed around the monsoon depression extended up to the west coast of India. Spatial variation of different weather parameters and their anomalies showed that many of the parameters were anomalously high during the second week of August 2018, when the torrential rainfall occurred. The simultaneous occurrence of all these conditions could have contributed to the extreme rainfall events and severe floods over Kerala.
PubDate: 2023-06-11
DOI: 10.1007/s00703-023-00974-1
- Impact of microphysics schemes on prediction of an extreme heavy rainfall
event over the Democratic People’s Republic of Korea: a case study using
WRF model-
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Abstract: Abstract The Kumchon region on the midlands of the Korean peninsula experienced the extreme rainfall on 29 August 2018 during the East Asian Summer Monsoon. In the present study, we investigated the sensitivity of this rainfall simulation of the Weather Research and Forecasting (WRF) model to the microphysics schemes. To this end, numerical simulations were performed for two different initial conditions using the WRF model with the grid resolution of 3 km and the different microphysics schemes (Lin, WDM6, Thompson, and Morrison). The initial conditions with two different initialization times were used to obtain a robust result. The model results were compared with the available surface observations. Our results of sensitivity simulations show that the microphysics are able to capture the observed rainfall pattern, but their skills are different significantly due to variation in mixing ratios of microphysics categories and associated dynamic and thermodynamic parameters. Compared to the observation, the Lin scheme displayed the best agreement in terms of the spatiotemporal distribution of heavy rainfall, while the performance of WDM6 scheme was the worst, for two initialization times. Model results suggested that the Lin scheme captured the spatiotemporal distribution of the different microphysics categories, and dynamic and thermodynamic parameters related to the intense rainfall event well. These results will be helpful to understand how the cloud microphysics affect rainfall prediction in the WRF model, and improve the forecast skills for heavy rainfall over the study region.
PubDate: 2023-06-05
DOI: 10.1007/s00703-023-00961-6
- Role of urban boundary layer dynamics and ventilation efficiency in a
severe air pollution episode in Tehran, Iran-
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Abstract: Abstract Tehran faces a significant health challenge due to severe air pollution episodes during wintertime, which are associated with high concentrations of fine particulate matter with a diameter less than 2.5 µm (PM2.5). In this study, we investigated meteorology conditions of one of the severe air pollution episodes, occurred from 27th December 2020 to 15th January 2021, using the Weather Research and Forecasting (WRF) model. To gain insights into this episode, we also modeled a clean episode for comparison. Model validation of land surface temperature using remote sensing showed acceptable performance as well as ground observations for other parameters. We then calculated the ventilation coefficient (VC) from the WRF outputs and analyzed the results statistically. Results indicate the severe reduction in both VC and planetary boundary layer height (PBLH) during the polluted episode. We further linked the decrease in PBLH and VC of the polluted episode to a high-pressure system above 1020 hPa. In contrast, the results for the clean episode indicate that the low-pressure system as low as 1010 hPa led to higher PBLH and VC than during the polluted episode. This low-pressure system favors the reduction of PM2.5 levels to lower than 21 μgm−3.
PubDate: 2023-05-27
DOI: 10.1007/s00703-023-00972-3
- Structural characteristics of typhoons Jebi (2018), Faxai (2019), and
Hagibis (2019)-
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Abstract: Abstract In recent years, Japan has experienced substantial damage from three intense typhoons: Jebi (2018), Faxai (2019), and Hagibis (2019). In this study, we provide a detailed description of the structure and synoptic environments of these typhoons, with particular focus on their frontal nature, temporal evolutions of the phase-space parameters, and the synoptic environments during their lifecycles. All three typhoons underwent phase changes at some point during their lifecycle before transitioning into extratropical cyclones. We found that their maximum intensities, as indicated by their maximum wind speed and minimum central pressure, occurred shortly after they transitioned from a cold-core to a warm-core structure. These typhoons displayed strong low-level convergence and upper-level divergence, along with favorable environmental conditions for strong convection before transitioning to extratropical cyclones. Our analysis suggests that the strong Typhoons Jebi and Hagibis had asymmetric structures with either deep warm or deep cold cores, whereas the relatively weak Typhoon Faxai had a symmetric deep warm core structure. Overall, our study provides valuable insights into the characteristics of intense typhoons and their transition to extratropical cyclones.
PubDate: 2023-05-22
DOI: 10.1007/s00703-023-00973-2
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