 Subjects -> METEOROLOGY (Total: 106 journals)
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- First Look of Surface Vegetation from the Advanced Geostationary Radiation
Imager (AGRI) onboard Fengyun-4B-
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Abstract: Abstract For many years, the status of surface vegetation has been monitored by using polar-orbiting satellite imagers such as Moderate Resolution Imaging Spectroradiometer (MODIS). However, limited availability of clear-sky samples makes the derived vegetation index dependent on multiple days of observations. High-frequency observations from the geostationary Fengyun (FY) satellites can significantly reduce the influence of clouds on the synthesis of terrestrial normalized difference vegetation index (NDVI). In this study, we derived the land surface vegetation index based on observational data from the Advanced Geostationary Radiation Imager (AGRI) onboard the FY-4B geostationary satellite. First, the AGRI reflectance of visible band and near-infrared band is corrected to the land surface reflectance by the 6S radiative transfer model. The bidirectional reflectance distribution function (BRDF) model is then used to normalize the AGRI surface reflectance at different observation angles and solar geometries, and an angle-independent reflectance is derived. The AGRI surface reflectance is further corrected to the MODIS levels according to the AGRI spectral response function (SRF). Finally, the daily AGRI data are used to synthesize the surface vegetation index. It is shown that the spatial distribution of NDVI images retrieved by single-day AGRI is consistent with that of 16-day MODIS data. At the same time, the dynamic range of the revised NDVI is closer to that of MODIS.
PubDate: 2023-08-01
- Shape Classification of Cloud Particles Recorded by the 2D-S Imaging Probe
Using a Convolutional Neural Network-
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Abstract: Abstract The airborne two-dimensional stereo (2D-S) optical array probe has been operating for more than 10 yr, accumulating a large amount of cloud particle image data. However, due to the lack of reliable and unbiased classification tools, our ability to extract meaningful morphological information related to cloud microphysical processes is limited. To solve this issue, we propose a novel classification algorithm for 2D-S cloud particle images based on a convolutional neural network (CNN), named CNN-2DS. A 2D-S cloud particle shape dataset was established by using the 2D-S cloud particle images observed from 13 aircraft detection flights in 6 regions of China (Northeast, Northwest, North, East, Central, and South China). This dataset contains 33,300 cloud particle images with 8 types of cloud particle shape (linear, sphere, dendrite, aggregate, graupel, plate, donut, and irregular). The CNN-2DS model was trained and tested based on the established 2D-S dataset. Experimental results show that the CNN-2DS model can accurately identify cloud particles with an average classification accuracy of 97%. Compared with other common classification models [e.g., Vision Transformer (ViT) and Residual Neural Network (ResNet)], the CNN-2DS model is lightweight (few parameters) and fast in calculations, and has the highest classification accuracy. In a word, the proposed CNN-2DS model is effective and reliable for the classification of cloud particles detected by the 2D-S probe.
PubDate: 2023-08-01
- Future Drought Changes in China Projected by the CMIP6 Models:
Contributions from Key Factors-
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Abstract: Abstract Model simulations show that drought may become more severe and widespread in the 21st century due to human-induced global warming. However, the contributions from the key factors to the model-projected drought changes in China have not yet been examined in detail. We used the self-calibrated Palmer Drought Severity Index with Penman–Monteith potential evapotranspiration (scPDSIpm) based on 10 model simulations selected from the Coupled Model Intercomparison Project Phase 6 (CMIP6). We investigated the contributions from precipitation (P), near-surface air temperature and specific humidity [Δ(T + q)], net surface longwave radiation (LW), net surface shortwave radiation (SW), and wind speed (WS) to the future changes in scPDSIpm, including the long-term mean, drying area, probability distribution function (PDF), drought frequency, and drought duration based on the scPDSIpm over China. Our results show that model-projected drying mainly occurs over southern China, whereas the dry areas under drought conditions increase from 20% to about 23%/30% under the two scenarios of the shared socioeconomic pathway (SSP2-4.5/SSP5-8.5) from 1985 to 2100, despite large uncertainties in individual projections partly due to internal variability. Drought frequency is projected to increases by about 10%–54% (15%–88%) under the SSP2-4.5 (SSP5-8.5) scenario by the late 21st century, along with increases in drought duration. These changes are accompanied by a decrease in the mean scPDSIpm and flattening of the PDFs. The changes in drying over southern China are mainly attributed to surface warming and the increased surface vapor pressure deficit (VPD), with small contributions from changes in the surface net radiation. The changes in wetting over northern China mostly result from increased precipitation along with a small wetting effect from the changes in wind speed.
PubDate: 2023-08-01
- Disastrous Persistent Extreme Rainfall Events of the 2022 Pre-Flood Season
in South China: Causes and Subseasonal Predictions-
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Abstract: Abstract Two persistent extreme rainfall events (PEREs) with record-breaking amounts of rainfall and long duration caused disastrous impact during the 2022 pre-flood season in South China. Atmospheric intraseasonal variability played a key role in triggering and maintaining both PEREs, but its major impact on each event was associated with different modes. For the first PERE (10–15 May; PERE1), the tropical and extratropical quasi-biweekly oscillations jointly contributed to the extreme rainfall intensity. In contrast, the long duration (6–21 June) of the heavy rainfall during the second PERE (PERE2) was closely related to prolonged convection and moisture transport anomalies induced mainly by the tropical 30–90-day variability. Subseasonal-to-seasonal predictions by the model of the ECMWF showed limited skill in relation to the rainfall intensity of PERE1 and PERE2 beyond 1–2 weeks. Further assessment suggested that the fidelity of the PERE predictions was linked to model skill in predicting the phase evolution and intensity of tropical and extratropical intraseasonal variabilities. Thus, efficient monitoring and accurate prediction of the various modes of atmospheric intraseasonal variability are fundamental to reducing the hazard associated with PEREs in South China.
PubDate: 2023-08-01
- Adaptive Statistical Spatial Downscaling of Precipitation Supported by
High-Resolution Atmospheric Simulation Data for Mountainous Areas of Nepal
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Abstract: Abstract In complex terrain regions, it is very challenging to obtain high accuracy and resolution precipitation data that are required in land hydrological studies. In this study, an adaptive precipitation downscaling method is proposed based on the statistical downscaling model MicroMet. A key input parameter in the MicroMet is the precipitation adjustment factor (PAF) that shows the elevation dependence of precipitation. Its value is estimated conventionally based on station observations and suffers sparse stations in high altitudes. This study proposes to estimate the PAF value and its spatial variability with precipitation data from high-resolution atmospheric simulations and tests the idea in Nepal of South Himalayas, where rainfall stations are relatively dense. The result shows that MicroMet performs the best with the PAF value estimated from the simulation data at the scale of approximately 1.5 degrees. Not only the value at this scale is qualitatively consistent with early knowledge obtained from intensive observations, but also the downscaling performance with this value is better than or comparable to that with the PAF estimated from dense station data. Finally, it is shown that the PAF estimation, although critical, cannot replace the importance of increasing input station density for downscaling.
PubDate: 2023-08-01
- Impact of Cold Spells on Ischemic Stroke Severity and Clinical Outcomes in
Tianjin, China-
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Abstract: Abstract There are several studies on the impact of extreme weather on the incidence and mortality of stroke, but the research on the effect of extreme weather events on severity and outcome of ischemic stroke is scarce. This study aimed to evaluate the impact of cold spells on the severity and clinical outcomes of patients with initial acute ischemic stroke in a hospital-based study. We enrolled 553 patients with initial ischemic stroke during the cold seasons between 2016 and 2019. Patients were separated into the mild stroke group and moderate-to-severe stroke group according to the National Institutes of Health Stroke Scale (NIHSS) of the U.S., and good outcome group and poor outcome group according to modified Rankin Scale (mRS) scores. There are nine different definitions of cold spells according to intensities and duration time. After adjustment for climate factors, air quality index, and common risk factors, it is found that cold spells were associated with moderate-to-severe neurological deficits and clinical outcomes in overall ischemic stroke patients. Furthermore, the delay effect for stroke severity started at the beginning of the cold wave (Lag 0) and lasted up to 14 days (Lags 0–14). In addition, when a cold spell was set as a daily mean temperature < 3rd or 5th percentile and with a duration ⩾ 2 or 3 consecutive days, cold spells had a significant impact on clinical outcomes, and there was a definite delay effect of at least 7 days (Lags 0–7) and it lasted up to 14 days (Lags 0–14). At last, we concluded that cold spells may be a contributory factor for more severe neurological deficits and worse outcomes in patients with initial ischemic stroke.
PubDate: 2023-08-01
- A Thorough Evaluation of the Passive Microwave Radiometer Measurements
onboard Three Fengyun-3 Satellites-
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Abstract: Abstract Microwave Radiometer Imager (MWRI) is a key payload of China’s second generation polar meteorological satellite, i.e., Fengyun-3 series (FY-3). Up to now, 5 satellites including FY-3A (2008), FY-3B (2010), FY-3C (2013), FY-3D (2018), and FY-3E (2021) have been launched successfully to provide multiwavelength, all-weather, and global data for decades. Much progress has been made on the calibration of MWRI and a recalibrated MWRI brightness temperature (BT) product (V2) was recently released. This study thoroughly evaluates the accuracy of this new product from FY-3B, 3C, and 3D by using the simultaneous collocated Global Precipitation Measurement (GPM) Microwave Imager (GMI) measurements as a reference. The results show that the mean biases (MBEs) of the BT between MWRI and GMI are generally less than 0.5 K and the root mean squares (RMSs) between them are less than 1.5 K. The previous notable ascending and descending difference of the MWRI has disappeared. This indicates that the new MWRI recalibration procedure is very effective in removing potential errors associated with the emission of the hot-load reflector. Analysis of the dependence of MBE on the latitude and earth scene temperature shows that MBE decreases with decreasing latitude over ocean. Furthermore, MBE over ocean decreases linearly with increasing scene temperature for almost all channels, whereas this does not occur over land. A linear regression fitting is then used to modify MWRI, which can reduce the MBE over ocean to be within 0.2 K. The standard deviation of error of GMI, FY-3B, and FY-3D MWRI BT data derived by using the three-cornered hat method (TCH) shows that GMI has the best overall performance over ocean except at 10.65 GHz where its standard deviation of error is slightly larger than that of FY-3D. Over land, the standard deviation of error of FY-3D is the lowest at almost all channels except at 89V. MWRI onboard FY-3 series satellites would serve as an important passive microwave radiometer member of the constellation to monitor key surface and atmospheric properties.
PubDate: 2023-08-01
- Unusual Evolution of the Multiple Eyewall Cycles in Super Typhoon
Hinnamnor (2022)-
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Abstract: Abstract Hinnamnor was the first super typhoon in the western North Pacific basin in 2022. It had several prominent characteristics, such as rapid intensification after its formation, three eyewall cycles, and a sudden recurvature of its track. Based on multi-source observational and reanalysis datasets, two secondary eyewall formation (SEF) cycles occurred during Super Typhoon Hinnamnor’s lifetime. The first SEF happened near the time when Hinnamnor achieved its maximum intensity, and it seems that its internal dynamics dominated the SEF process after the development of shear-induced asymmetric spiral rainbands. The merger of a tropical depression with Hinnamnor led to a continuous increase in both its inner-core size and outer-core circulation, causing generation of the second SEF. It is inferred that the external and internal dynamics worked together during the second SEF process. The concentric eyewall structure maintained for approximately 84 h under the moderate vertical wind shear. Also, unique changes in intensity accompanied the two structural changes.
PubDate: 2023-08-01
- Zonally Asymmetric Temperature Trends near the Northern Middle and High
Latitude Stratopause during Winter-
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Abstract: Abstract The temperature trend near the stratopause is rarely evaluated owing to the limited long-term observations of global temperature. In this study, the spatial patterns of the temperature trends near the northern stratopause are investigated by using satellite and reanalysis datasets. Our analysis reveals a zonally asymmetric temperature trend pattern near the northern mid-to-high latitude stratopause during January, and this pattern underwent an evident transition around the 2000s. From 1980 to 2003, there was a cooling trend in the Western Hemisphere and a warming trend in the Eastern Hemisphere. In contrast, a reversed zonally asymmetric temperature trend pattern existed in the east-west direction from 2003 to 2020. Although the warming trends are statistically insignificant, they contrasted with the overall cooling trend in the upper stratosphere due to ozone depletion and an increase in well-mixed greenhouse gases in recent decades. The zonally asymmetric temperature trends were induced by the transition in the intensity of quasi-stationary planetary wavenumber 1 (wave 1) near the stratopause. The increasing (decreasing) trend of the intensity of wave 1 enhanced (weakened) its meridional temperature advection near the stratopause before (after) the 2000s; consequently, a zonally asymmetric temperature trend pattern exists in the east–west direction near the stratopause. The transition in the intensity of the stratospheric wave 1 around the 2000s is most likely caused by the transition in the intensity of wave 1 activity in the troposphere.
PubDate: 2023-08-01
- Efficiently Improving Ensemble Forecasts of Warm-Sector Heavy Rainfall
over Coastal Southern China: Targeted Assimilation to Reduce the Critical
Initial Field Errors-
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Abstract: Abstract Warm-sector heavy rainfall events over southern China are difficult to accurately forecast, due in part to inaccurate initial fields in numerical weather prediction models. In order to determine an efficient way of reducing the critical initial field errors, this study conducts and compares two sets of 60-member ensemble forecast experiments of a warm-sector heavy rainfall event over coastal southern China without data assimilation (NODA) and with radar radial velocity data assimilation (RadarDA). Yangjiang radar data, which can provide offshore high-resolution wind field information, were assimilated by using a Weather Research and Forecasting (WRF)-based ensemble Kalman filter (EnKF) system. The results show that the speed and direction errors of the southeasterly airflow in the marine boundary layer over the northern South China Sea may primarily be responsible for the forecast errors in rainfall and convection evolution. Targeted assimilation of radial velocity data from the Yangjiang radar can reduce the critical initial field errors of most members, resulting in improvements to the ensemble forecast. Specifically, RadarDA simulations indicate that radial-velocity data assimilation (VrDA) can directly reduce the initial field errors in wind speed and direction, and indirectly and slightly adjust the initial moisture fields in most members, thereby improving the evolution features of moisture transport during the subsequent forecast period. Therefore, these RadarDA members can better capture the initiation and development of convection and have higher forecast skill for the convection evolution and rainfall. The improvement in the deterministic forecasts of most members results in an improved overall ensemble forecast performance. However, VrDA sometimes results in inappropriate adjustment of the initial wind field, so the forecast skill of a few members decreases rather than increases after VrDA. This suggests that a degree of uncertainty remains about the effect of the WRF-based EnKF system. Moreover, the results further indicate that accurate forecasts of the convection evolution and rainfall of warm-sector heavy rainfall events over southern China are challenging.
PubDate: 2023-08-01
- Variation in Sunshine Duration and Related Aerosol Influences at
Shangdianzi GAW Station, China: 1958–2021-
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Abstract: Abstract Sunshine duration (SD) is adopted widely to study global dimming/brightening. However, long-term simultaneous measurements of SD and closely related impact factors require further analysis to elucidate how and why SD has varied during the past decades. In this study, a long-term (1958–2021) SD data series obtained from the Shangdianzi Global Atmosphere Watch (GAW) station in China was analyzed to detect linear trends, climatic jumps, and climatic periods in SD using linear fitting, the Mann–Kendall trend test, and the continuous wavelet transform method. Annual SD exhibited steady dimming (−67.3 h decade−1) before 2010, followed by a period of brightening (189.9 h decade−1) during 2011–2020. An abrupt jump in annual SD occurred in 1995, and the annual SD anomaly exhibited significant oscillation with ∼3-yr periodicity during 1960–1978. Partial least squares analysis revealed that annual SD anomaly was associated with variations in relative humidity, gale days, cloud cover, and black carbon (BC). Further analysis of the clear-sky daily sunshine percentage (DSP) and simultaneous measurements of aerosol properties, including aerosol optical depth, aerosol extinction coefficient, single scattering albedo (SSA), BC, and total suspended particulates, suggested that variation in DSP was affected primarily by aerosol scattering and absorption. Furthermore, the hourly clear-sky SD at high aerosol loading was approximately 60% and 56% of that at middle and low aerosol loadings, respectively. The pattern of diurnal variation in clear-sky hourly SD, as well as the actual values, can be affected by the fine particulate concentration, aerosol extinction coefficient, and SSA.
PubDate: 2023-08-01
- Verification of a Modified Nonhydrostatic Global Spectral Dynamical Core
Based on the Dry-Mass Vertical Coordinate: Three-Dimensional Idealized
Test Cases-
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Abstract: Abstract The newly developed nonhydrostatic (NH) global spectral dynamical core is evaluated by using three-dimensional (3D) benchmark tests with/without moisture. This new dynamical core differs from the original Aladin-NH like one in the combined use of a dry-mass vertical coordinate and a new temperature variable, and thus, it inherently conserves the dry air mass and includes the mass sink effect associated with precipitation flux. Some 3D dry benchmark tests are first conducted, including steady state, dry baroclinic waves, mountain waves in non-sheared and sheared background flows, and a dry Held–Suarez test. The results from these test cases demonstrate that the present dynamical core is accurate and robust in applications on the sphere, especially for addressing the nonhydrostatic effects. Then, three additional moist test cases are conducted to further explore the improvement of the new dynamical core. Importantly, in contrast to the original Aladin-NH like one, the new dynamical core prefers to obtain simulated tropical cyclone with lower pressure, stronger wind speeds, and faster northward movement, which is much closer to the results from the Model for Prediction Across Scales (MPAS), and it also enhances the updrafts and provides enhanced precipitation rate in the tropics, which partially compensates the inefficient vertical transport due to the absence of the deep convection parameterization in the moist Held–Suarez test, thus demonstrating its potential value for full-physics global NH numerical weather prediction application.
PubDate: 2023-06-01
- Impact of the Return Flow on Heavy Pollution in Winter over the
Beijing–Tianjin–Hebei Region-
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Abstract: Abstract In North China, the return flow (RF) refers to the airflow at the rear of an inshore high pressure, bringing southerly wind to the Beijing–Tianjin–Hebei (BTH) region when the high pressure pushes deeper from coast into the mainland. Many studies have pointed out the significant contribution of southerly anomalies to the transport and accumulation of pollutants in the BTH region. However, the relationship between RF and heavy pollution episodes (HPEs) in the BTH region requires more in-depth analysis, and this study will focus on this topic. By objectively identifying RFs and HPEs based on the ERA5 reanalysis data and observed hourly PM2.5 concentration data during 9 winters of 2012–2020, it is found that almost two-thirds of the HPEs in the BTH region coincide with the occurrence of RFs. The northward transport of warm and humid air is stronger in the HPEs under RF conditions, whereas the sinking motion and the decrease in boundary layer height dominate the HPEs without any RF. We then classify the RFs into north and south types by a demarcation line of 32°N. Both types of RFs are featured with a zonal circulation pattern, stable atmosphere, and southerly airflow favoring the development of HPEs, but the south type RFs bring warmer and wetter air masses to the BTH region, forming a more stable and thicker inversion layer and causing more severe HPEs. With occurrences of the RF, low-level winds are observed to accelerate, and the ageostrophic wind components contribute mainly to this acceleration. During the presence of RFs, the kinetic energy generation at the high level decreases, and the weakened downward transport results in weak low-level northerly winds, weak turbulence, and a shallow boundary layer, thus hindering the diffusion of atmospheric pollutants in the BTH region.
PubDate: 2023-06-01
- Characteristics of Precipitation in China Associated with Tropical
Cyclones over the Bay of Bengal-
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Abstract: Abstract In comparison with the number of studies into the impact on precipitation in China of tropical cyclones (TCs) over the western North Pacific, investigation of the effect of TCs in the Bay of Bengal (BoB) on precipitation in China is lacking. In this study, precipitation in China associated with TCs over the BoB was divided into direct rainfall induced by TC cloud clusters and indirect rainfall related to the long-distance transport of TC water vapor. We partitioned the BoB TC-related rainfall that occurred during 2000–2018 in China and analyzed its statistical features. It was found that 40 of the 67 (60%) TCs that occurred over the BoB exerted influence on rainfall in China. Direct rainfall was mainly distributed over the southeastern Tibetan Plateau and Southwest China, while indirect rainfall was distributed widely with two high-value centers: one over Yunnan Province and the other over the area south of the middle–lower reaches of the Yangtze River. The highest mean daily rainfall amount of direct TC precipitation appeared in northern Yunnan Province and southeastern Tibet, while that of indirect TC precipitation occurred eastward of 110°E. During the bimodal period of peak occurrence of BoB TCs in May and October–November, the annual mean amount, intensity, and number of days of rainfall in China related to BoB TCs were generally greater in May, e.g., the mean daily rainfall amount was twice that in October–November, except at stations in southeastern Tibet. In comparison with the BoB TCs that induced heavy rainfall in China in early summer, the TCs in autumn had a more southwestward mean position and a more asymmetric structure, with the long axis oriented in the northeast–southwest direction. Heavy rainfall induced by BoB TCs occurred mainly over southeastern Tibet and provinces south of the middle–lower reaches of the Yangtze River in early summer and over Yunnan and Sichuan provinces in autumn, mostly in response to circulation patterns of a “northern trough with a southern TC” and of “convergence of two high pressure systems,” respectively.
PubDate: 2023-06-01
- Extended-Range Precursors for Summer Consecutive Extreme Rainfall in the
Yangtze River Valley Related to Intraseasonal Variations of the
Pacific–Japan Teleconnection-
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Abstract: Abstract In summer, the Yangtze River valley (YRV) in central–eastern China frequently suffers consecutive extreme rainfall (CER) events, causing floods and huge damages. On the daily timescale, our previous study has shown that the Pacific–Japan (PJ) teleconnection is related to the CER events over the YRV, and is a source for long-term (lead time of about 10 days) forecasts of CER events. To facilitate extended-range (lead time of about 20 days) prediction of CER, in the present study, we use the band-pass filter for the PJ teleconnection to keep only the prolonged atmospheric circulation information at the intraseasonal timescale and try to identify more advanced precursors for the CER events over the YRV. Power spectrum analysis was implemented on 9-day sliding mean of the precipitation anomalies. It is found that summer precipitation in YRV has significant 10–40-day oscillations, and the CER events over the YRV are affected by the intraseasonal oscillation (ISO) of the PJ teleconnection. When the ISO of the PJ teleconnection enters its positive phase, it is favorable for CER events to occur. Dynamic diagnoses and model experiments demonstrate that the ISO of the PJ teleconnection is attributed to the intraseasonal convective activities and diabatic heating around the Philippines, which generate significant northward energy dispersion and propagation of Rossby waves up to 16 days prior to occurrences of the CER events in the YRV. The ISO of the PJ teleconnection and the convective activities in the tropical South Asia provide significant and earlier precursors for extended-range forecasts of the CER events along the YRV.
PubDate: 2023-06-01
- Relationships between Springtime Sea Surface Temperatures in Different
Indian Ocean Domains and Various Asian Monsoons from Late Spring to the
Following Summer-
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Abstract: Abstract We investigate the relative importance of spring sea surface temperatures (SSTs) in different Indian Ocean (IO) domains, especially the northern and southern IO, for the development and intensity of the Asian summer monsoon. By performing unsupervised neural network analysis, the self-organizing map, we extract distinct patterns of springtime IO SST. The results show that the uniform warming (cooling) of the southern IO plays a crucial role in the warming (cooling) of both the basin-wide IO and tropical IO. The southern IO thus well represents the associations of basin-wide IO and tropical IO with the Asian summer monsoon, and is instrumental in the relationship between the IO and summer monsoon. A warming in the southern IO is closely related to the weakening of large-scale meridional monsoon circulation in May and summer (June–August), including suppression of the South Asian monsoon development in May and the East Asian monsoon in summer. On the other hand, a warming in the northern IO appears to be associated with an earlier South Asian monsoon onset and a stronger East Asian monsoon. In summer, the connection of the springtime IO SST with the South Asian monsoon weakens, but that with the East Asian monsoon strengthens. Finally, a robust negative correlation is found between the warming of various IO domains and the development and intensity of the Southeast Asian monsoon.
PubDate: 2023-06-01
- Characteristics of Cloud Water Resource and Precipitation Efficiency of
Hydrometeors over Northwest China-
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Abstract: Abstract Understanding the characteristics of cloud water resource (CWR) and precipitation efficiency of hydrometeors (PEh) is imperative for the application of CWR in Northwest China. The atmospheric precipitable water (PW) in all four seasons and clouds and PEh in summer were studied with ERA-5 and CloudSat data in this region. The results show that topography, especially in the Tibetan Plateau, exerts significant impacts on the precipitation and PW in summer, since large amounts of clouds are distributed along the mountain ranges. The study region is divided into four typical areas: the monsoon area in eastern Northwest China (NWE), the Qilian Mountains area (QM), the Tian-shan Mountains area (TM), and the Source of Three Rivers area (STR). Over the four areas, cloud top height (6.3 km) and cloud base height (3.3 km) over NWE are higher, and precipitating clouds are thicker (7 km) in the single-layer clouds. Liquid water content decreases with increasing altitude, while the ice water content first increases and then decreases. Liquid water path is higher over NWE (0.11 kg m−2) than over TM and STR (0.05 kg m−2), and the ice water path is mainly concentrated within the range of 0.025–0.055 kg m−2. The PEh values are distributed unevenly and affected evidently by the terrain. Although the PEh values in the four typical areas (0.3–0.6) are higher than those in other regions, the CWR is relatively abundant and has a higher exploitation potential. Therefore, it is well-founded to exploit CWR for alleviating water shortages in these areas of Northwest China in summer.
PubDate: 2023-06-01
- Ecological Assessment of Oxygen Balance: A Case Study of China’s
Natural Oxygen Bars-
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Abstract: Abstract Ecological assessment plays a vital role in sustainable development of the environment, and thus exploration of specific and integrated ecological assessment methods has become a critical task. In this study, based on the concept of oxygen balance and by accommodating both natural factors and socioeconomic elements, we establish an oxygen (O2) balance index (OBI), i.e., the ratio of the O2 production from the ecosystem to the O2 consumption by human behavior, based on the net primary productivity (NPP), fuel consumption, gross domestic production (GDP), population data, and so on. The results show that the spatial distributions of OBI in China are intimately correlated to the regional vegetation and socioeconomic development. The estimated OBI values are then validated by statistical data from 27 counties in China, and it is found that the OBI reflects the ecological environment status well. Moreover, the average OBI values derived from 190 natural oxygen bars in China reveal extreme imbalance between O2 production and consumption in highly developed regions, especially in the cities, in contrast to good O2 balance in areas with high-quality ecological status and less industrialization. The findings from this study have quantitatively captured the regional ecological quality, providing guidance for sustainable natural and socioeconomic developments in local areas of China.
PubDate: 2023-06-01
- New Version of the CMA-GFS Dynamical Core Based on the
Predictor–Corrector Time Integration Scheme-
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Abstract: Abstract The operational numerical weather prediction system established by the China Meteorological Administration (CMA), based on the Global/Regional Assimilation and Prediction System (GRAPES) model, adopts the classical semi-implicit semi-Lagrangian (SISL) time integration algorithm. This paper describes a major upgrade to the dynamical core of the CMA global forecast system (CMA-GFS), which was successfully incorporated into operation in 2020. In the upgrade, the classical SISL is further developed into a predictor–corrector scheme, a three-dimensional (3D) reference profile instead of the original isothermal reference profile is applied when implementing the semi-implicit algorithm, and a hybrid terrain-following vertical coordinate system is also applied. The new version of the dynamical core greatly improves the model performance, the time integration reaches second-order accuracy, the time step can be extended by 50%, and the efficiency is greatly improved (by approximately 30%). Atmospheric circulation simulation is systematically improved, and deviations in temperature, wind, and humidity are reduced. The new version of the dynamical core provides a solid foundation for further development of the entire operational system of the CMA.
PubDate: 2023-06-01
- Effects of Large-Scale Climatic Oscillations on the Variability of the
Indian Summer Monsoon Rainfall-
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Abstract: Abstract In India, large-scale climatic oscillations have strong influences on the Indian summer monsoon rainfall (ISMR), which plays a crucial role in India’s agricultural production and economic growth. However, there are limited studies in India that explore the influences of decadal and multidecadal oscillations on the ISMR and associated El Niño–Southern Oscillation (ENSO). Therefore, in this study we carried out a comprehensive and detailed investigation to understand the influences of ENSO, Pacific decadal oscillation (PDO), and Atlantic multidecadal oscillation (AMO) on ISMR across different regions in India. The statistical significance of ISMR associated with different phases (positive/warm and negative/cold) of ENSO, PDO, and AMO (individual analysis), and combined ENSO–AMO, and ENSO–PDO (coupled analysis) were analysed by using the nonparametric Wilcoxon Rank Sum (WRS) test. The individual analysis results indicate that in addition to the ENSO teleconnection, AMO and PDO significantly affect the spatial patterns of ISMR. Coupled analysis was performed to understand how the phase shift of PDO and AMO has modulated the rainfall during El Niño and La Niña phases. The results indicate that the La Niña associated with a positive PDO phase caused excessive precipitation of about 21%–150% in the peninsular, west–central, and hilly regions compared to the individual effect of ENSO/PDO/AMO on ISMR; similarly, the west–central, coastal, and northwest regions received 15%–56% of excessive rainfall. Moreover, during the El Niño combined with PDO positive (AMO positive), above-normal precipitation was observed in hilly, northeast, and coastal (hilly, northeast, west–central, and coastal) regions, opposite to the results obtained from the individual ENSO analysis. This study emphasizes the importance of accounting the decadal and multidecadal forcing when examining variations in the ISMR during different phases of ENSO events.
PubDate: 2023-06-01
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