 Subjects -> METEOROLOGY (Total: 106 journals)
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- Climatic characteristics of mesoscale convective systems in the warm
season in North China-
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Abstract: Abstract In this study, a total of 339 mesoscale convective systems (MCSs) are obtained in North China using the temperature of brightness blackbody (TBB) data from the FY-2E in the warm season from 2010 to 2018. The number of meso-α-scale convective systems (MαCSs) is much more than that of meso-β-scale convective systems (MβCSs). The number of mesoscale elongated convective systems (MECSs) is more than that of mesoscale circular convective systems (MCCSs). Most MCSs occur in July and August, which have the widest influence range, the longest duration, and the strongest convection. The MαCS develops slowly and weakens rapidly. The diurnal variation of MαCSs presents a bimodal distribution, most of MαCSs form in the afternoon, while some of MαCSs form in the evening. The MCSs activities in the warm season of North China are concentrated in two belts, namely, the east–west-oriented belt along Henan Province, Shandong Province and the Yellow Sea, and the south–north-oriented belt along central-western Shandong, Tianjin City, the west of Bohai Sea and the northeast of Hebei Province. MCSs mainly move eastward, and only some MECSs move southwestward and northwestward. The easterly and northerly moving MCSs are mainly affected by the steering flow, while the southerly moving MCSs are mainly affected by storm propagation. The MCSs of North China mainly form in the high temperature, high humidity and high energy area, with favorable dynamic conditions, such as middle-level trough or vortex, low-level shear line, surface inverted trough or surface convergence line, and the terrain. Meanwhile, the MCS pregnant environment is often accompanied by low-level jet and relatively strong vertical wind shear.
PubDate: 2023-03-16
- A diagnostic study of heavy rainfall events in upper Ganga and Sharda
river basins, India-
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Abstract: Abstract Upper Ganga (UG) and Sharda are two river basins in Uttarakhand, India that are situated in the western Himalayan region. Previous studies revealed that these basins are prone to high seasonal rainfall (more than 100 cm) and substantial interannual variations during the southwest monsoon season. However, synoptic situations causing heavy rainfall events in the basins are not properly understood. The present study attempts to understand the synoptic situations causing heavy rainfall events in the basins using synoptic analogue and rainfall data from India Meteorological Department, followed by a diagnostic assessment using ERA5 reanalysis data. The synoptic systems associated with heavy rainfall events in the basins are found to be different. Heavy rainfall events in UG are triggered by the movement of mid-latitude systems (trough in westerlies) towards north India which provide convergence at middle and upper tropospheric levels. These systems strengthen when they are supported by the northward progression of the monsoon trough (especially the western end of the monsoon trough) and embedded cyclonic circulations. We found that heavy rainfall events in UG are associated with the development of a cyclonic circulation extending up to the mid-troposphere/low-pressure system in the northwest Bay of Bengal. The mid-tropospheric divergence over this cyclonic circulation system feeds moisture to the convergence due to the southward extended trough in the mid-latitude westerlies and caters to the formation of heavy rainfall events in the basin. Heavy rainfall events in Sharda are associated with the movement of low-pressure systems from the Bay of Bengal towards the region, which provides anomalous convergence in the lower levels. It is supported by a trough in the mid-latitude westerlies in the mid and upper tropospheric levels, which increases the convergence at lower and mid-tropospheric levels and leads to heavy rainfall events in the basin. This study reveals the tropical-midlatitude interaction and its role in the heavy rainfall events over the western Himalayan region.
PubDate: 2023-03-15
- Exploring the asymmetry and rate of SAT warming over the global land area
under the 1.5 °C and 2 °C climate change targets-
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Abstract: Abstract The Paris Agreement establishes targets for the increase in global mean temperature of 1.5 °C and 2 °C, relative to pre-industrial levels. Recent studies suggest that the climate change impacts of these two goals are markedly different, and the additional 0.5 °C increase in the global mean surface air temperature (SAT) may lead to drastic, non-linear increases in the extreme and average temperatures of most regions. In this study, we use model results from the Coupled Model Intercomparison Project 5 (CMIP5) to illustrate the asymmetric nature of the warming trends that will result over the global land area under these two climate change targets. The results show that the SAT increase reaches 1.5 °C by 2040 (2040 ± 6), considering RCP2.6 to RCP8.5, whereas the SAT increase reaches 2.0 °C by 2060 (2060 ± 12), considering RCP4.5 to RCP8.5. The SAT increase over land is meridionally and zonally asymmetric, especially in the Northern Hemisphere. What’s global warming and rising concentrations of emissions will exacerbate the asymmetric warming from north to south especially over land. In addition to the longitudinal changes, the magnitude of the SAT increase at higher latitudes is significantly greater than that of comparable areas at middle to low latitudes. Additionally, the time of the SAT increase over the high-latitude land areas occurs much earlier than elsewhere. In addition, the difference in the timing of this onset in the longitudinal direction is substantial, but the difference in the zonal direction is small. Furthermore, the SAT increase over most of the global land area reaches 1.5 °C before the middle of twenty-first century and reaches 2.0 °C before 2070. In addition, over 20% of the global land area, the SAT increase reaches 1.5 °C before 2006, whereas almost none of the land area exhibits a change of 2.0 °C before 2006.
PubDate: 2023-03-14
- Application on using the infinite medium vector Green’s function for
polarized radiation in a Rayleigh-scattering atmosphere-
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Abstract: Abstract The radiative transfer equation has wide application fields, such as atmospheric optics, oceanography, biomedical physics, and optical tomography. This paper presents the investigation of the vector radiative transfer equation for polarized radiation transport in optically semi-infinite, homogeneous, Rayleigh-scattering atmosphere with no interior source using an analytical approximation. The spatial attenuation coefficient, the outward-to-inward flux ratio, and the mean cosine, which were defined in terms of the total intensity component, I, were calculated for Rayleigh-scattering case using the infinite medium Green’s function. The behaviors of these parameters were obtained as a function of the optical depth.
PubDate: 2023-03-10
- Surface atmospheric electric field variability on the Qinghai-Tibet
Plateau-
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Abstract: Abstract The variability in the atmospheric electric field needs to be understood before considering the properties of the atmospheric electrostatic distribution on the Tibetan Plateau. The relationship between each meteorological parameter and the atmospheric electric field should be carefully considered. In this article, atmospheric electric field observations and their effects from weather conditions at Gar Station (80.13°E, 32.52°N, altitude 4259 m) for the period from November 2021 to October 2022 are presented. After defining strict and reliable criteria for fair weather, the authors show the diurnal variation curve of the average fair weather atmospheric electric field, which has “double peaks and double valleys”. How various meteorological conditions affect variability in the atmospheric electric field and comparisons between the Gar curve and “Carnegie curves” are also revealed.
PubDate: 2023-02-22
- Assessing the performance of WRF ARW model in simulating heavy rainfall
events over the Pune region: in support of operational applications-
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Abstract: Abstract This study evaluates the impact of the Planetary Boundary layer (PBL) on rainfall simulated by the Weather Research and Forecasting (WRF) model during extreme rainfall event cases over an urban city. This is accomplished by producing a heavy rainfall event forecast using the WRF model with five varying PBL scenarios (ACM2, YSU, MYJ, QNSE, MYNN) but otherwise identical model configuration. The study examined the role of PBL in modulating rainfall characteristics by investigating the impacts of PBL on forecast skills with particular reference to rainfall. The PBL scheme plays a crucial role and can significantly alter the spatial pattern and magnitudes of rainfall simulated by the model. Results showed that the QNSE boundary layer scheme substantially improved the magnitudes and spatial pattern of rainfall simulated by the model. The model’s ability was cross-checked with this setup to capture the other two heavy rainfall events over Pune city and was found satisfactory. The current model setup could capture the spatial distribution and the magnitude of rainfall compared with satellite data and observation over point locations. These findings are highly relevant to highlight the dependency of the model on parameterization schemes to forecast extreme rainfall events accurately.
PubDate: 2023-02-11
- Correction to: Macro‑ and microphysical characteristics of snowfall and
non‑snowfall clouds in the West Tianshan Mountains of China based on
cloud radar-
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PubDate: 2023-02-10
- Characteristics of various radiative fluxes: global, tilted, direct, and
diffused radiation—a case study of Nigeria-
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Abstract: Abstract A proper understanding of what the earth’s surface receives when sun rays leave the sun’s disk is important as this informs the decisions made by meteorologist and the likes in utilizing solar energy. In this pursuit, this study was performed by taking stations from each geological region in Nigeria. Data were obtained for the Global Horizontal Irradiation (GHI), Global Tilted Irradiation (GTI), Direct Normal Irradiation (DNI), and Diffused Ratio (Kd) for 12 years (2005–2016). The Diffused Horizontal Irradiation (DHI) was calculated and the results were presented. It was concluded that the latitude, local weather conditions, elevation, etc. were major factors that contributed to the amount of solar energy that can be received in a particular location. Results showed that for the locations in the northern region of Nigeria where the local weather conditions are less humid (characterized by clear skies), lower diffused irradiation (DHI) and higher direct irradiation (DNI) were observed; the reverse is the case for the locations around the south of Nigeria. This shows that global solar irradiation or GHI would be received more in the northern locations than in the south, leading to the importance of understanding the GTI which involves tilting the Solar PVs or receptors to angles that would receive more DNI than DHI. These angles were displayed and we concluded that solar trackers may not be necessary when users understand the presented results. Results can be adopted for other locations with the same latitudes around the globe.
PubDate: 2023-02-03
- Dynamical characteristics of Amphan and its impact on COVID-19 cases in
Bangladesh-
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Abstract: Abstract In May 2020, a category-5 tropical cyclone (TC) Amphan formed in the Bay of Bengal and struck the coasts of India and Bangladesh. In this study, the relevant dynamic characteristics and aftermaths of Amphan are documented. Through detailed investigation of the reanalysis and observation data, spatiotemporal varying characteristics of the atmospheric and oceanic parameters during the Amphan propagation process were analyzed. Due to a wide range of high sea surface temperature anomaly, Amphan developed rapidly and ultimately led to the local heavy precipitation and strong winds in the coastal areas during its passage. It is also noted that the recorded wave height, wave period, and current speed all amplified when Amphan passed by and the characteristics of wave and current directions are also consistent with the temporal variation of the corresponding wind field. Meanwhile, Amphan occurred in accompany with the ongoing COVID-19 pandemic. In Khulna Division of Bangladesh, the number of newly confirmed COVID-19 cases increased rapidly after Amphan landing, which however was almost nil before the event, indicating there might exist a possible correlation between Amphan and the intensive outbreak of the local COVID-19, and particular attentions should be paid to deal with the multi-type, coexisting disasters if different or even conflicting measures are required.
PubDate: 2023-01-23
- Comparison between warm-sector and frontal heavy rainfall events in South
China and the objective classification of warm-sector heavy rainfall
events-
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Abstract: Abstract In this study, a total of 402 warm-sector heavy rainfall (WSHR) and 528 frontal heavy rainfall (FHR) events are identified by using the hourly precipitation data of 124 national rain gauge stations in South China from 1981 to 2020. The frequency of heavy rainfall events in South China presents an overall increasing trend, mainly due to the increase of WSHR events in Guangxi. The monthly frequency of FHR events in Guangxi is always higher than that in Guangdong from April to September, particularly in July, while WSHR events occur more (less) frequently in Guangdong than in Guangxi in April, May, and August (June and July). The FHR events mainly start around 0000 BST (Beijing Standard Time), while the start time of WSHR events is relatively evenly distributed from 2300 to 0300 BST. Synoptic circulations of WSHR events are objectively classified into five types, which reveals the difference of intensity and location of synoptic-scale systems (the western Pacific subtropical high, vortex, shear line, synoptic low-level jet, boundary layer jet) and precipitation among the five-type events. The occurrence frequency of Type 1 WSHR events in Guangxi peaks in June, while that of Type 2 varies greatly in Guangxi and Guangdong. The start time of Type 1 WSHR events has two peaks at 0100 BST and 0800 BST, while the start time of other four types is mainly within 2300 BST–0400 BST. The mean duration of each type WSHR events is about 10–25 h with shortest for Type 4 WSHR events and longest for Type 5.
PubDate: 2022-12-26
DOI: 10.1007/s00703-022-00949-8
- Mapping of solar insolation using air temperature in tropical and
mountainous environments-
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Abstract: Solar energy potential maps facilitate the process of making decisions regarding the installation of photovoltaic solar energy systems. However, the lack of recorded in-situ solar irradiance information hinders decision-making in this field of study. Therefore, in this study, the number of solar irradiance sample points was increased, using temperature-based empirical models such as that from Hargreaves and Samani and a new approach based on the logistic model, and the performance of four spatial interpolation techniques was assessed in tropical and mountainous environments. The analysis concluded that the Hargreaves and Samani model is better for the Pacific zone, whereas the logistic model is better for the Andean and Amazon zones. In addition, the ordinary Kriging method was found to be the best interpolation technique, as it presents a lower bias. Graphical abstract 
PubDate: 2022-12-26
DOI: 10.1007/s00703-022-00945-y
- One-hour-ahead solar radiation forecasting by MLP, LSTM, and ANFIS
approaches-
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Abstract: Abstract The use and importance of renewable energy sources (RES) have been increasing every passing year as fossil fuels will soon be depleted. Within this context, solar-photovoltaic (PV) is the most preferred energy type among RES. The PV has uncertain power output as its output depends on solar radiation, which is heavily influenced by environmental factors, so the prediction of solar radiation plays a crucial role in integrating these plants into the electricity grid. For the short-term 1-h-ahead solar radiation prediction, four time-series methods were implemented in this study: long short-term memory (LSTM) network, multilayer perceptron (MLP), and adaptive neuro-fuzzy inference system (ANFIS) with grid partition (GP), and fuzzy c-means (FCM). Root mean square error (RMSE), correlation coefficient (R), and mean absolute error (MAE) were used as statistical error criteria. The obtained results by the LSTM, MLP, ANFIS-FCM and ANFIS-GP models were assessed by comparing with the actual data. Considering the testing procedure, the best MAE values were found to be 53.37 W/m2, 58.45 W/m2, 61.68 W/m2, and 78.17 W/m2 for the LSTM, ANFIS-FCM, MLP, and ANFIS-GP, respectively. Results showed that the LSTM model in 1-h-ahead solar radiation prediction yielded the best results among all four models with high accuracy.
PubDate: 2022-12-16
DOI: 10.1007/s00703-022-00946-x
- Linkages between Madden–Julian oscillation and drought events over
Kenya-
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Abstract: Abstract Increased frequencies and intensities of extreme weather events have negatively impacted climate-sensitive socio-economic sectors in Kenya and larger Equatorial East Africa (EEA). Madden–Julian oscillation (MJO) influence intra-seasonal weather variability over Kenya although less attention has been given to its effect on extreme weather events such as droughts and floods, which have increased in frequency and intensity. Outgoing Longwave Radiation (OLR) was used in this work as proxy data for rainfall to study the geographical distribution and circulation anomalies associated with MJOs and their impacts on extreme weather events. Extreme weather events are identified using the self-calibrating Palmer Drought Severity Index (sc-PDSI), based on sc-PDSI, 2013/2014 and 2017/2018 as the drought and flood years, respectively. The background power spectral analysis reveals that MJOs are more dominant during the March–May (MAM) season than other seasons. The variance analysis depicted that the maximum power of MJO-filtered OLR is cantered within the tropical Indian Ocean, maritime continent and the tropical Pacific Ocean. Upper tropospheric (200 hPa) wind signatures give a clear Matsuno-Gill-type circulation compared to the lower tropospheric wind flows. Thus, the signatures can be used to develop a dynamic MJO index for prediction purposes. There exists a weak direct relationship between MJO and sc-PDSI; however, the influence may result from its modulation of atmospheric circulation as illustrated by the wind and velocity potential patterns before and after the passage of the convective MJO phase.
PubDate: 2022-12-14
DOI: 10.1007/s00703-022-00948-9
- Quantifying the evolving role of intense precipitation runoff when
calculating soil moisture trends in east Texas-
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Abstract: Abstract Eastern Texas straddles a precipitation zone that transitions from semi-arid grasslands to the humid, rainy conditions of the northern Gulf Coast. While several studies have quantified the changing magnitude and frequency of daily extreme events, the paucity of hourly datasets have limited insight into how the growing proportion of rainfall exceeding hourly soil infiltration capacity has and will exacerbate the state’s droughts. This paper builds on previous analysis, deploying algorithms with a temporal dimension to calculate soil moisture scarcity from evapotranspiration and precipitation data based on FAO-56 methodology and then introduces a daily estimate of the proportion of precipitation that flows off the ground surface rather than replenishing moisture deficits for soils with three different infiltrative capacities at 12 observation sites. The comparison of subsequent time-series regression analyses showed that absorptive soils in east Texas have experienced modest, though mostly statistically insignificant, acceleration in drought trends after the incorporation of hourly rainfall intensity data: for the 24 soil samples (out of 36) with saturated hydraulic conductivity \(\left( {K_{{{\text{sat}}}} } \right)\) rates greater than 4.5 mm per hour, 14 had accelerated drying trends, five showed no change, and the remaining five displayed more gradual changes relative to their baseline trend magnitudes.
PubDate: 2022-12-14
DOI: 10.1007/s00703-022-00947-w
- Observations and mesoscale forecasts of the life cycle of rapidly
intensifying super cyclonic storm Amphan (2020)-
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Abstract: Abstract Super cyclonic storm Amphan (2020), formed over the Bay of Bengal, has been forecasted using the mesoscale model WRF to examine the rapid intensification (RI) features in the model forecast. The special surface and upper air weather observational campaigns were arranged from ISRO’s Balasore observatory during the life cycle of Amphan. Along with these observations, forecasts have been validated with the available surface and upper air observations along the east coast of India, the GPM-IMERG rainfall observations, and the ECMWF Reanalysis-5 (ERA-5) reanalysis. The dynamical parameters, viz. low-level convergence, middle tropospheric humidity, and diabatic heating in the middle troposphere, have been compared with reanalysis. It is seen that up to 124-h forecasts of track and intensities have significantly improved And the surface and upper air parameters forecast is reliable for up to 48 h. The study showed that the high SST in the range 30–31 °C along the track of the TC, TCHP range of 60–70 kJ cm−2, ~ 100% Mid-tropospheric relative humidity (MTRH), enhanced diabatic heating in the rainband region. Intense rainfall in the front left quadrant of the system favored the rapid intensification of Amphan. Because of the large size, high shear (10–25 ms−1) is ineffective in hindering the system’s intensification process. The wind variation during the system’s landfall is also well captured, and 24 h forecast agrees with the observed data. The appropriate representation of vertical wind shear required for realistic simulation of axisymmetric, asymmetric, and landfall dynamics, is also evident from campaign observations.
PubDate: 2022-12-09
DOI: 10.1007/s00703-022-00944-z
- Idealized simulations of the boundary layer thermal structure for a
landfalling tropical cyclone-
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Abstract: Abstract The evolution of the boundary layer kinematic and thermodynamic structure for a landfalling tropical cyclone (TC) is examined using a high-resolution multi-level boundary layer model in storm-relative coordinates. For a moving storm near a coastal boundary, it is shown that motion-induced asymmetries and land-induced asymmetries develop which affect the steady-state thermal structure of the tropical cyclone boundary layer (TCBL). Motion-induced asymmetries generate enhanced convergence and reduced thermal stability (due to enhanced surface heat fluxes) in the front-right quadrant of the vortex. In contrast, the presence of land generates a wavenumber-1 asymmetry in equivalent potential temperature \({\theta }_{e}\) by advecting low \({\theta }_{e}\) air offshore and high \({\theta }_{e}\) air onshore. The collective impact of these asymmetries depends upon (i) the orientation of the storm motion vector with respect to the coastline, (ii) the location of the coastline relative to the TC center, and (iii) the land–sea thermal and moisture contrast. When the storm motion vector is oriented parallel to the coastal boundary, the land–sea thermal contrast, coupled with the local pressure gradient, produces a narrow band of positive vertical vorticity that stabilizes the TCBL inside the band and destabilizes the TCBL outside the band. However, when the storm motion vector is oriented perpendicular to the coastal boundary, the enhanced frictional convergence initiates an anomalous secondary circulation ahead of the vortex, and the horizontal vertical velocity gradient from this secondary circulation, coupled with the vertical shear from boundary layer friction, generates vertical vorticity via tilting and stretching. The combined effect of these land-induced asymmetries is to produce enhanced precipitation in the front-left quadrant of the vortex and a frontal structure to the rear of the vortex due to the formation of a sharp \({\theta }_{e}\) gradient in agreement with previous observational studies.
PubDate: 2022-12-02
DOI: 10.1007/s00703-022-00943-0
- Determination of suitable thermodynamic indices and prediction of
thunderstorm events for Eastern India-
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Abstract: Abstract We have studied the upper air RSRW data of 00 UTC during the pre-monsoon season, i.e. March–May of 2016–2018 for 6 capital cities viz. Kolkata, Bhubaneswar, Guwahati, Patna, Ranchi in the Eastern part of India and one island station, Port Blair. We have analyzed thermodynamic stability indices to identify the indices which have been most suitable for the prediction of thunderstorm events for each location. Based on the consensus of suitable indices and considering the spatial variation, we have proposed a scheme for predicting whether there would be any thunderstorm at a particular location within 24 hours. Verification has been carried out for 2019–2020 depending on availability of data and the performance of the proposed scheme has been compared with existing latest operational methods in India. We find that the proposed scheme can predict thunderstorms with reasonable accuracy and has better performance, mostly than that of existing operational methods.
PubDate: 2022-11-28
DOI: 10.1007/s00703-022-00942-1
- Impact of sea-breeze circulation on the characteristics of convective
thunderstorms over southeast India-
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Abstract: Abstract The impact of Sea-breeze circulation on the convective thunderstorms over the southeast coast of Tamilnadu, India is studied using the Weather Research and Forecasting (WRF) model. High-resolution (2-km) simulations are conducted with WRF for two severe thunderstorm events on 24 April 2015 in summer 22 July 2015 in the southwest monsoon. Surface observations of Automated Weather Stations (AWS), gridded accumulated rainfall, radiosonde, and Doppler Weather Radar (DWR) reflectivity products are used for model evaluation. Simulations indicated that the moisture convergence in the sea breeze frontal zone and the presence of lower atmospheric wind shear during sea breeze are the main factors for the initiation of deep convection and intensification of the thunderstorms. Simulations reveal that the thunderstorms developed in summer are more intensive due to more intense and deep-sea breeze circulation cells developing under weak synoptic flow during summer compared to monsoon. Results show that simulated summer thunderstorms are associated with higher CAPE, lower CIN, stronger vertical motion in association with a stronger convergence, higher buoyancy and larger low-level wind shear and lower upper air shear compared to the monsoon thunderstorms. The presence of stronger lower atmospheric wind shear during summer sea-breeze favours the development of strong and deep convection compared to the monsoon season. Results also showed a simulation of more solid hydrometeors (ice, snow and graupel) due to intense convection in summer compared to the monsoon season.
PubDate: 2022-11-28
DOI: 10.1007/s00703-022-00941-2
- Study of micrometeorological characteristics of the atmospheric surface
layer over a tropical coastal station in Goa-
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Abstract: Abstract This study presents turbulence characteristics of the atmospheric surface layer (ASL) observed during March 2015 to February 2016 over a tropical coastal site in Goa (15.46°N, 73.83°E), India. The primary datasets utilized are the 3D wind components and sonic temperature from sensors mounted on a 32-m meteorological tower at 10 and 20 m heights respectively. Eddy correlation technique has been adopted to study turbulence characteristics and is investigated under the framework of Monin–Obukhov Similarity Theory (MOST). Results revealed that normalized wind variances ( \({\upsigma }_{\mathrm{i}=\mathrm{u},\mathrm{ v},\mathrm{ w}}/{\mathrm{u}}_{*}\) ) follow the ‘1/3’ power law in highly unstable and stable conditions and approach constant values close to near-neutral conditions. In the neutral limit, it is found that \({\upsigma }_{\mathrm{u}}/{\mathrm{u}}_{* }>{\upsigma }_{\mathrm{v}}/{\mathrm{u}}_{* }>{\upsigma }_{\mathrm{w}}/{\mathrm{u}}_{*}\) . The normalized temperature variances ( \({\upsigma }_{\mathrm{T}}/{\mathrm{T}}_{*}\) ) followed \({\left(\mathrm{z}/\mathrm{L}\right) }^{-1/3}\) during unstable conditions and approach a constant value in the stable limit. The correlation coefficients for momentum (heat) flux with stability were small (high) under strong unstable and stable conditions. Also, the values of momentum flux increased as it approaches neutral conditions which are consistent with studies reported over coastal/urban locations.
PubDate: 2022-11-22
DOI: 10.1007/s00703-022-00940-3
- Continuous monitoring of the atmospheric boundary layer (ABL) height from
micro pulse lidar over a tropical coastal station, Kattankulathur (12.82°
N, 80.04° E)-
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Abstract: Abstract The continuous monitoring of the atmospheric boundary layer (ABL) height and its diurnal variation over the coastal station is generally a challenging task due to the frequent occurrence of the thermal internal boundary layer (TIBL), neutral boundary layer, and boundary layer with a strong residual layer (RL). The wavelet covariance transform (WCT) method provides robust estimates of the ABL height; however, it fails for the cases with strong RL and TIBL. Therefore, an improved fuzzy logic algorithm has been developed incorporating the sea breeze membership function besides the six membership functions used in previous studies. Fuzzy logic classifies the signals according to the membership functions based on the quality score of the individual extracted features, making it a robust method for identifying the different types of ABL. In this study, 78 days of micropulse lidar (MPL) observations over Kattankulathur (12.82° N, 80.04°E) during 2018 are utilized to identify the diurnal variation of the ABL using a fuzzy logic algorithm. Out of 78 cases, we have observed 12 convective or unstable ABL cases, 10 neutral ABL, 24 convective cases with strong RL, and 32 convective cases dominated by TIBL. For the unstable ABL, both fuzzy logic and WCT detect a similar diurnal pattern. For the neutral ABL, the stable boundary layer (SBL) does not evolve, and hence again, both fuzzy logic and WCT detect a similar ABL pattern. However, for the strong RL and TIBL cases, the ABL height obtained using the WCT method overestimates the fuzzy logic algorithm. The ABL height for various diurnal patterns obtained using fuzzy logic algorithm compares well with radiosonde observations at 05:30 IST and 17:30 IST. The daytime mean ABL height obtained using fuzzy logic compares well with the Indian monsoon data assimilation and analysis (IMDAA) re-analysis product (generated for the Indian monsoon region); however, IMDAA underestimates the night-time mean ABL height.
PubDate: 2022-11-17
DOI: 10.1007/s00703-022-00938-x
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