Occurrence Of Heavy Precipitation Research Articles

Mesoscale Characteristics of Exceptionally Heavy Rainfall during 4–6 May 2023 in Jiangxi, China

A long-lasting rainfall event exceeding historical extremes took place in Jiangxi, China, from May 4 to 6, 2023. Because of the concentrated duration of precipitation, it led to significant water accumulation in the northern, central, and southern regions of Jiangxi. The objective of this study was to investigate the weather mechanisms underlying this extreme rainstorm in Jiangxi. By examining detailed observational data, the mesoscale weather characteristics and environmental conditions of the event can be obtained. These findings offer valuable insights for future weather forecasting and warnings. It was observed that after the Huanghuai cyclone moved eastward into the sea, the cold air on its western side shifted northward and converged with the warm, moisture-laden air mass in Hunan and Jiangxi provinces. This convergence of air masses triggered the heavy rainstorm event. The peak precipitation period occurred from midnight on May 5 to 0800 BJT on May 6. Concerning the macroscopic precipitation characteristics, multiple mesoscale convective systems (MCSs) originated in Hunan during this period and progressed eastward along the shear line toward the central part of Jiangxi. As for the microscopic precipitation features, the total precipitation amount was closely linked to the duration of heavy rain droplets. The rainfall distribution in the raindrop spectrum also served as a valuable reference for understanding the persistence and size of precipitation. The temporal pattern of the combined reflectivity echo along 27.5° N indicated that from 2000 BJT on May 5 to the early morning of May 6, there was a rapid development of a weaker MCS after passing through the Luoxiao Mountains. This development resulted in a “train effect” in the central region of Jiangxi. The presence of a 200 hPa divergence area, high vertical ascent rate, and abundant water vapor contributed to the formation of a narrow area of heavy rainstorms in central Jiangxi. Additionally, the falling area of heavy rain coincided with the front of the 500 hPa low trough. In the northern part of Jiangxi, the occurrence of heavy precipitation was influenced by the equivalent temperature front area. Favorable conditions, including water vapor, dynamics, and thermal factors, further supported the occurrence of heavy precipitation.

Occurrence of heavy precipitation influenced by solar wind high-speed streams through vertical atmospheric coupling

A tendency of heavy rainfall-induced floods in Canada to follow arrivals of solar wind high-speed streams (HSSs) from coronal holes is observed. Precipitation events during the winter, including extreme freezing rain events in the province of New Brunswick, also tend to occur following HSSs. More direct evidence is provided using the satellite-based gridded precipitation dataset Integrated Multi-satellitE Retrievals for GPM (IMERG) in the superposed epoch analysis of high-rate precipitation. The results show an increase in the high-rate daily precipitation occurrence over Canada following arrivals of major HSSs. This is consistent with previously published results for other mid-latitude geographic regions. The ERA5 meteorological reanalysis is used to evaluate the slantwise convective available potential energy (SCAPE) that is of importance in the development of storms. The role of the solar wind-magnetosphere-ionosphere-atmosphere coupling, mediated by globally propagating aurorally excited atmospheric gravity waves releasing the conditional symmetric instability in the troposphere leading to convection and precipitation, is proposed.

Present and Future of Heavy Rain Events in the Sahel and West Africa

Gridding precipitation datasets for climate information services in the semi-arid regions of West Africa has some advantages due to the limited spatial coverage of rain gauges, the limited accessibility to in situ gauge data, and the important progress in earth observation and climate modelling systems. Can accurate information on the occurrence of heavy precipitation in this area be provided using gridded datasets? Furthermore, what about the future of heavy rain events (HRE) under the shared socioeconomic pathways (SSP) of the Inter-Sectoral Impact Model Intercomparison Project (i.e., SSP126 and SSP370)? To address these questions, daily precipitation records from 17 datasets, including satellite estimates, interpolated rain gauge data, reanalysis, merged products, a regional climate model, and global circulation models, are examined and compared to quality-controlled in situ data from 69 rain gauges evenly distributed across West Africa’s semi-arid region. The results show a consensus increase in the occurrence of HRE, between observational and gridded data. All datasets showed three categories of HRE every season, but these categories had lower intensities and an overstated frequency of occurrence in gridded datasets compared to in situ rain gauge data. Eight out of 17 databases (~47%) show significant positive trends and only one showed a significant negative trend, indicating an increase in HRE for all categories in this region. The future evolution of HRE considered under the shared socioeconomic pathways SSP1-2.6 and SSP3-7.0, showed a trend toward the intensification of these events. In fact, the mean of the ensemble of the models showed significant changes toward higher values in the probability distribution function of the future HRE in West Africa, which may likely trigger more floods and landslides in the region. The use of gridded data sets can provide accurate information on the occurrence of heavy precipitation in the West African Sahel. However, it is important to consider the representation of heavy rain events in each data set when monitoring extreme precipitation, although in situ gauge records are preferred to define extreme rainfall locally.

대기의 강(Atmospheric River)이 남한의 스톰과 강수 특성에 미치는 영향

Atmospheric rivers (ARs) that are characterized by an elongated plume of intense vertically-integrated water-vapor transport (IVT) in the atmosphere, are critical in the occurrence of heavy precipitation and hydrologic extremes, especially in the mid-latitudes, in addition to the poleward water-vapor transport. Although ARs affect regional hydrology and can lead to natural disasters, few studies have examined the relationship between ARs and continuous precipitation events like storms. This study analyzes the climatology of AR-related precipitation in South Korea (SK) on the basis of storm events. In SK, AR storms undergo a well-defined annual cycle with a peak in July and outnumber non-AR storms in all months. AR (non-AR) storm duration exhibits an annual cycle with the peak in August (no systematic annual cycle). AR storms are related to larger (smaller) IVT over East Asian coastal regions (western North Pacific) compared to non-AR storms. The IVT difference appears to lead to precipitation differences such that AR storms dominate non-AR storms in monthly and annual-total precipitation, especially in summer. The effects of AR storms on monthly storm-total and storm-mean precipitation are strongest in the central (July) and southern (August) parts of SK and decrease gradually towards the north. Seasonal variations in the occurrence and intensity of AR storms and associated daily precipitation in SK are characterized by a small number of heavy-precipitating AR storms in June and September and a large number of heavy-precipitating AR storms in July and August.

Overview towards improved understanding of the mechanisms leading to heavy precipitation in the western Mediterranean: lessons learned from HyMeX

Abstract. Heavy precipitation (HP) constitutes a major meteorological threat in the western Mediterranean (WMed). Every year, recurrent events affect the area with fatal consequences for infrastructure and personal losses. Despite this being a well-known issue widely investigated in the past, open questions still remain. Particularly, the understanding of the underlying mechanisms and the modeling representation of the events must be improved. One of the major goals of the Hydrological Cycle in the Mediterranean Experiment (HyMeX; 2010–2020) has been to advance knowledge on this topic. In this article, we present an overview of the most recent lessons learned from HyMeX towards an improved understanding of the mechanisms leading to HP in the WMed. The unique network of instruments deployed as well as the use of finer model resolutions and coupled models provided an unprecedented opportunity to validate numerical model simulations, develop improved parameterizations, and design high-resolution ensemble modeling approaches and sophisticated assimilation techniques across scales. All in all, HyMeX, and particularly the science team heavy precipitation, favored the evidencing of theoretical results, the enrichment of our knowledge on the genesis and evolution of convection in a complex topography environment, and the improvement of precipitation forecasts. Illustratively, the intervention of cyclones and warm conveyor belts in the occurrence of heavy precipitation has been pointed out, and the crucial role of the spatiotemporal distribution of atmospheric water vapor for the understanding and accurate forecast of the timing and location of deep convection has been evidenced, as has the complex interaction among processes across scales. The importance of soil and ocean conditions and the interactions among systems were highlighted, and such systems were specifically developed in the framework of HyMeX to improve the realism of weather forecasts. Furthermore, the benefits of cross-disciplinary efforts within HyMeX have been a key asset in bringing our knowledge about heavy precipitation in the Mediterranean region a step forward.

Projection of hydroclimate extreme indices over the Indochina region under climate change using a large single‐model ensemble

AbstractResults from the multiple‐realization, single‐model ensemble called “d4PDF” were used to generate hydroclimate indices for present and future climates over the Indochina region. The model performed reasonably well in capturing the reference precipitation characteristics of the present climate (1951–2010), in particular the seasonal pattern (e.g., JJA and SON) and intensity‐based indices such as SDII, R95p, Rx1D, and Rx3D. Under the +4 K future simulation conditions for 2051–2110, comprising six prescribed sea‐surface temperature scenarios, substantial and statistically significant increases in precipitation frequency (R10 and R20) and intensity (SDII, Rx1D, and Rx3D) were projected over the Indochinese Peninsula with a high degree of consistency. However, there were greater uncertainties in the changes significance of mean precipitation either during early dry‐season (DJF) or late monsoon (SON) indices demonstrated by results of the parametric U test in some river catchments, such as the Chao Phraya, Red River, central Mekong, lower Irrawaddy, and Salween Basins, where the projection consistencies in a positive change direction were less than 50%. Comparison of basin‐wide empirical probability distributions of precipitation indices pointed to a robust increase in the frequency of the occurrence of heavy precipitation in intensity indices (e.g., Rx1D, Rx3D, and SDII). The relationship between d4PDF precipitation and total runoff generation outputs from the land surface component was investigated. The results show a high degree of temporal correspondence across the region under the present climate in several seasonal and intensity indices, except during the dry period (DJF and MAM). Finally, we found that ε P(P, R) of the annual and seasonal climatological indices of the future climate were always positive and larger than unity, with a median ε P(P, R) of 1.28–2.04. The results strongly reaffirm the role of rainfall as the main driver of runoff changes due to its faster response relative to change in precipitation at the Indochina Region.

Changing Spatiotemporal Patterns of 5- and 10-Day Illinois Heavy Precipitation Amounts, 1900–2018

AbstractThis study examined the spatiotemporal variability associated with 5-/10-day heavy precipitation amounts for 48 high-quality and long-duration (1900–2018) stations in Illinois. The top five seasonal and annual heavy precipitation amounts for each duration were determined and examined for each station. Annual and seasonal spatial patterns generally showed a trend of decreasing precipitation amounts as one moved northward through Illinois. Spatial distributions of the top seasonal amounts exhibited the highest values in boreal spring and summer, with the lowest values during winter. Temporal analysis of the top five 5- and 10-day amounts from 1900 to 2018 indicated an increasing trend with a higher frequencies in the 2000–18 period for spring, summer, winter, and annual time periods (statistically significant for spring and annual). No trend was found in autumn heavy precipitation occurrence. In addition, heavy precipitation events were examined in the context of the background atmospheric environment using the Twentieth Century Reanalysis. Event-averaged precipitable water values were shown to scale linearly with total precipitation in the winter season. Low-level circulation fields indicate that the most widespread heavy rain episodes occur when a synoptic anticyclone is positioned off the coast of the eastern United States. Results from this study suggest that design values used for hydrologic structures should be reevaluated given recent observations.

Statistical analysis of very high-resolution precipitation data and relation to atmospheric circulation in Central Germany

Abstract. The cumulative occurrence of heavy precipitation and flood events during recent years in various Central European locations emphasises the urgent need to improve extreme rainfall observations and forecasts. Precipitation gauges based on a weighing system allow the recording of intense short-term precipitation events with a very high temporal resolution (down to 1 min). In this study, observational data that were collected during the period 2000 to 2016 for 126 stations of two corresponding measuring networks in the Central German state of Hesse were investigated for the first time to answer the following questions: (1) Are the recorded high-resolution precipitation data plausible and comparable between both networks? (2) Which atmospheric circulation patterns were specifically prone to produce short-term intense precipitation events? Although the two networks are equipped with the same measuring technology, systematic differences concerning their maximum 1 min precipitation amounts occur, which may be explained by different instrumental software settings. We could minimise those discrepancies by accumulating the existing 1 min data to 15 min. Subsequently, the 15 min daily maximum values and accumulated daily sums were analysed regarding the impact of large-scale atmospheric circulation patterns, based on the well-known “Großwetterlagen” classification. We identified a clear connection between atmospheric circulation and heavy precipitation over Hesse, while indicating some differences between daily (24 h) and sub-daily (15 min) events. High daily precipitation sums often relate to westerlies and central cyclones, while intense short-term events are frequently generated by warm-humid continental air from southern and eastern Europe as well as trough conditions, where the trough's core is found west of the study area. Our results underline the importance of expanding and enhancing high-resolution precipitation observations in Germany as well as other countries.

Climatological moisture sources for the Western North American Monsoon through a Lagrangian approach: their influence on precipitation intensity

Abstract. This work examines the origin of atmospheric water vapor arriving to the western North American monsoon (WNAM) region over a 34-year period (1981–2014) using a Lagrangian approach. This methodology computes budgets of evaporation minus precipitation (E−P) by calculating changes in the specific humidity of thousands of air particles advected into the study area by the observed winds. The length of the period analyzed (34 years) allows the method to identify oceanic and terrestrial sources of moisture to the WNAM region from a climatological perspective. During the wet season, the WNAM region itself is on average the main evaporative source, followed by the Gulf of California. However, water vapor originating from the Caribbean Sea, the Gulf of Mexico, and terrestrial eastern Mexico is found to influence regional-scale rainfall generation. Enhanced (reduced) moisture transport from the Caribbean Sea and the Gulf of Mexico from 4 to 6 days before precipitation events seems to be responsible for increased (decreased) rainfall intensity on regional scales during the monsoon peak. Westward propagating mid- to upper-level inverted troughs (IVs) seem to favor these water vapor fluxes from the east. In particular, a 200 % increase in the moisture flux from the Caribbean Sea to the WNAM region is found to be followed by the occurrence of heavy precipitation in the WNAM area a few days later. Low-level troughs off the coast of northwestern Mexico and upper-level IVs over the Gulf of Mexico are also related to these extreme rainfall events.

NUMERICAL PREDICTION OF AN EXTREME RAINSTORM OVER THE PEARL RIVER DELTA REGION ON 7 MAY 2017 BASED ON WRF-ENKF

An ensemble Kalman filter based on the Weather Research and Forecasting Model (WRF-EnKF) is used to explore the effectiveness of the assimilation of surface observation data in an extreme local rainstorm over the Pearl River Delta region on 7 May 2017. Before the occurrence of rainstorm, the signals of weather forecasts in this case are too weak to be predicted by numerical weather model, but the surface temperature over the urban area are high. The results of this study show that the wind field, temperature, and water vapor are obviously adjusted by assimilating surface data of 10-m wind, 2-m temperature, and 2-m water vapor mixing ratio at 2300 BST 6 May, especially below the height of 2 km. The southerly wind over the Pearl River Delta region is enhanced, and the convergence of wind over the northern Guangzhou city is also enhanced. Additionally, temperature, water vapor mixing ratio and pseudoequivalent potential temperature are obviously increased over the urban region, providing favorable conditions for the occurrence of heavy precipitation. After assimilation, the predictions of 12-h rainfall amount, temperature, and relative humidity are significantly improved, and the rainfall intensity and distribution in this case can be successfully reproduced. Moreover, sensitivity tests suggest that the assimilation of 2-m temperature is the key to predict this extreme rainfall and just assimilating data of surface wind or water vapor is not workable, implying that urban heat island effect may be an important factor in this extreme rainstorm.

Synoptic patterns and sounding‐derived parameters associated with summertime heavy rainfall in Beijing

Heavy precipitation in Beijing is modulated by both synoptic forcings and local thermodynamic characteristics of troposphere, which has yet to be well known. This study investigated the large‐scale synoptic patterns and local sounding features associated with the summertime heavy precipitation in Beijing, based on long‐term surface meteorological observations, radiosonde measurements, in combination of reanalysis data from 2008 to 2017. The results show that the heavy rainfall occurs more frequently in late July, which is associated with the movement of subtropical anticyclone. The sounding parameters during the heavy rainfall days are examined as well. It is found that the heavy rainfall is often related to favourable convective conditions characterized by abundant water vapour and high unstable energy. The soundings for around 45% of heavy rainfall days in Beijing exhibit the pattern of “thin tube” (TT), and those for ~25 and ~20% of heavy rainfall days show the patterns of “loaded gun” (LG) and “inverted V” (IV), respectively. On average, the rainfall amount of TT is 55.8 mm/day, which is ~3 mm/day (~15 mm/day) higher than that of LG (IV). The more frequent and heavier rainfall observed for TT pattern is due to the high values of precipitable water and wind shear. On the large scale, three dominant synoptic patterns associated with heavy rainfall in Beijing have been identified using the T‐mode principle component analysis. These synoptic patterns are all characterized by prevailing southerly winds within the lower troposphere, resulting in water vapours being easily transported from southern regions to Beijing, which in turn favours the occurrence of heavy precipitation. These dominant synoptic patterns and thermodynamic characteristics associated with the heavy rainfall in Beijing revealed in this study have important implications for better understanding of heavy rainfall in the North China Plain.

An event synchronization method to link heavy rainfall events and large‐scale atmospheric circulation features

ABSTRACTHeavy rainfall, floods and other hydroclimatic extremes may be related to specific states of organization of the atmospheric circulation. The identification of these states and their linkage to local extremes could facilitate a physically meaningful quantification of local extremes in future climates and could allow forecasting extremes conditioned on the large‐scale atmospheric state. A novel methodology is presented that combines non‐linear, non‐parametric methods to link heavy precipitation events (HPEs) to atmospheric circulation states. Using daily rainfall data for the period 1951–2015 from 37 gauges in the Lazio region in Italy, HPEs are defined. For the same period, two atmospheric variables, namely, the 850 hPa geopotential height field and the integrated vapour transport (IVT), are derived from reanalysis data. The geopotential configurations driving heavy precipitation in the region are identified by combing self‐organized maps and event synchronization. First, a finite number of representative geopotential configurations is identified. Rainfall gauges are pooled into clusters, which show synchronized occurrence of heavy precipitation. Furthermore, geopotential configurations are identified, which tend to drive HPEs. For these geopotential states, the probability of HPE occurrence as a function of IVT is calculated through a local logistic regression model. Finally, it is explored whether the identified patterns are related to the occurrence of atmospheric rivers, which govern the atmospheric humidity transport from the tropics and subtropics to Europe. The relation found demonstrates the reliability of the proposed methodology.

Twenty-First-Century Changes in U.S. Regional Heavy Precipitation Frequency Based on Resolved Atmospheric Patterns

Precipitation-gauge observations and atmospheric reanalysis are combined to develop an analogue method for detecting heavy precipitation events based on prevailing large-scale atmospheric conditions. Combinations of atmospheric variables for circulation (geopotential height and wind vector) and moisture (surface specific humidity, column and up to 500-hPa precipitable water) are examined to construct analogue schemes for the winter [December–February (DJF)] of the “Pacific Coast California” (PCCA) region and the summer [June–August (JJA)] of the Midwestern United States (MWST). The detection diagnostics of analogue schemes are calibrated with 1979–2005 and validated with 2006–14 NASA Modern-Era Retrospective Analysis for Research and Applications (MERRA). All analogue schemes are found to significantly improve upon MERRA precipitation in characterizing the occurrence and interannual variations of observed heavy precipitation events in the MWST. When evaluated with the late twentieth-century climate model simulations from phase 5 of the Coupled Model Intercomparison Project (CMIP5), all analogue schemes produce model medians of heavy precipitation frequency that are more consistent with observations and have smaller intermodel discrepancies than model-based precipitation. Under the representative concentration pathways (RCP) 4.5 and 8.5 scenarios, the CMIP5-based analogue schemes produce trends in heavy precipitation occurrence through the twenty-first century that are consistent with model-based precipitation, but with smaller intermodel disparity. The median trends in heavy precipitation frequency are positive for DJF over PCCA but are slightly negative for JJA over MWST. Overall, the analyses highlight the potential of the analogue as a powerful diagnostic tool for model deficiencies and its complementarity to an evaluation of heavy precipitation frequency based on model precipitation alone.

Sea breeze and precipitation over Hainan Island

The relationship between sea breeze and precipitation over Hainan Island is investigated, along with consideration of the effects of orography, synoptic wind and environmental conditions, using a period (2011–2015) of high‐resolution observational data, ERA‐Interim reanalysis data, and numerical experiments. The results show that the combined effect of mountain–plain and plain–sea thermal contrasts plays a major role in promoting sea‐breeze occurrence on Hainan Island. Although the sea‐breeze convergence tendency favours precipitation formation during October to March, the low humidity and convective available potential energy (CAPE), stable atmospheric stratification, high free convection level (LFC) and strong vertical wind shear in northeasterlies during this period notably inhibit the occurrence of heavy precipitation on Hainan Island. On the contrary, large amounts of precipitation over Hainan Island during April to September arise from high humidity and CAPE, unstable atmospheric stratification, low LFC and weak vertical wind shear associated with southwesterlies; additionally, the sea‐breeze front (SBF) has a convergence tendency under weak synoptic winds. In the context of the synoptic wind, these strong precipitations are prone to occur on the mountain leeward side, likely because of a strong leeward‐side SBF, which could be enhanced considerably by the orography; however, heavy precipitation seldom occurs on the mountain windward side, likely due to weak lifting motion associated with weak synoptic winds and a less significant windward‐side SBF. Because of these effects, pronounced precipitation is apt to occur over the east and west coasts, and propagates northeastward or northward with the steering of the southwesterlies and the development of SBFs in the north part of the island, during April to August. Whereas in September similar amounts of precipitation tend to occur over the southeast and southwest coasts, and expand locally with the influence of the easterlies and the inland penetration of SBFs.

A desertificação no Alto Sertão de Sergipe/Brasil: abordagem na perspectiva das vulnerabilidades socioambientais

A desertificação é um dos cenários de degradação que repercute em todo sistema socioambiental. Tem origem na dinâmica natural e nas ações antropogênicas, visto que a natureza passa a ser explorada de forma exacerbada pela racionalidade econômica, dilapidando mais do que preservando, o que intensifica a crise ambiental. As áreas vulneráveis a desertificação são as que apresentam maior fragilidade climática (distribuição pluvial de forma irregular, ocorrência de precipitações torrenciais e/ou períodos muito secos); solos rasos propensos à erosão, mudanças de organização e de produção espacial (enfraquecimento econômico e emigrações) pelas atividades humanas. Nesse sentido, o objetivo de se desenvolver esta pesquisa é compreender os processos de vulnerabilidades a desertificação no Alto Sertão de Sergipe, tendo por base uma bibliografia pertinente ao tema e levantamentos de campo na área de estudo. No Alto Sertão Sergipano a desertificação é dinâmica e se desenvolve sobre um ecogeossistema frágil, cuja vulnerabilidade é aqui analisada sob o enfoque geográfico.

Influence of North Pacific SST on heavy precipitation events in autumn over North China

AbstractThe characteristics of heavy precipitation occurrence in autumn (the month of September) over North China are investigated using daily observational data. Results indicate that heavy precipitation events experienced a significant decadal increase in 2000/2001. Further investigation reveals a close connection between heavy precipitation occurrence and simultaneous North Pacific SST. The SST anomaly over the North Pacific can result in intensification of the western North Pacific subtropical high and increased water vapor transport from the tropical ocean, which benefits the occurrence of heavy precipitation over North China. However, the key region of North Pacific SST influencing heavy precipitation events over North China was different in the periods 1960–2000 and 2001–2014, being located over the eastern Ocean to China in the first period but more eastward in the second period. This drift in the key region of SST is partly responsible for the decadal increase in heavy precipitation events over N...

SHORT-TERM PRECIPITATION OCCURRENCE PREDICTION FOR STRONG CONVECTIVE WEATHER USING FY2-G SATELLITE DATA: A CASE STUDY OF SHENZHEN,SOUTH CHINA

Abstract. Short-term precipitation commonly occurs in south part of China, which brings intensive precipitation in local region for very short time. Massive water would cause the intensive flood inside of city when precipitation amount beyond the capacity of city drainage system. Thousands people’s life could be influenced by those short-term disasters and the higher city managements are required to facing these challenges. How to predict the occurrence of heavy precipitation accurately is one of the worthwhile scientific questions in meteorology. According to recent studies, the accuracy of short-term precipitation prediction based on numerical simulation model still remains low reliability, in some area where lack of local observations, the accuracy may be as low as 10%. The methodology for short term precipitation occurrence prediction still remains a challenge. In this paper, a machine learning method based on SVM was presented to predict short-term precipitation occurrence by using FY2-G satellite imagery and ground in situ observation data. The results were validated by traditional TS score which commonly used in evaluation of weather prediction. The results indicate that the proposed algorithm can present overall accuracy up to 90% for one-hour to six-hour forecast. The result implies the prediction accuracy could be improved by using machine learning method combining with satellite image. This prediction model can be further used to evaluated to predicted other characteristics of weather in Shenzhen in future.

SHORT-TERM PRECIPITATION OCCURRENCE PREDICTION FOR STRONG CONVECTIVE WEATHER USING FY2-G SATELLITE DATA: A CASE STUDY OF SHENZHEN,SOUTH CHINA

Short-term precipitation commonly occurs in south part of China, which brings intensive precipitation in local region for very short time. Massive water would cause the intensive flood inside of city when precipitation amount beyond the capacity of city drainage system. Thousands people’s life could be influenced by those short-term disasters and the higher city managements are required to facing these challenges. How to predict the occurrence of heavy precipitation accurately is one of the worthwhile scientific questions in meteorology. According to recent studies, the accuracy of short-term precipitation prediction based on numerical simulation model still remains low reliability, in some area where lack of local observations, the accuracy may be as low as 10%. The methodology for short term precipitation occurrence prediction still remains a challenge. In this paper, a machine learning method based on SVM was presented to predict short-term precipitation occurrence by using FY2-G satellite imagery and ground in situ observation data. The results were validated by traditional TS score which commonly used in evaluation of weather prediction. The results indicate that the proposed algorithm can present overall accuracy up to 90% for one-hour to six-hour forecast. The result implies the prediction accuracy could be improved by using machine learning method combining with satellite image. This prediction model can be further used to evaluated to predicted other characteristics of weather in Shenzhen in future.

The climate of daily precipitation in the Alps: development and analysis of a high‐resolution grid dataset from pan‐Alpine rain‐gauge data

ABSTRACTIn the region of the European Alps, national and regional meteorological services operate rain‐gauge networks, which together, constitute one of the densest in situ observation systems in a large‐scale high‐mountain region. Data from these networks are consistently analyzed, in this study, to develop a pan‐Alpine grid dataset and to describe the region's mesoscale precipitation climate, including the occurrence of heavy precipitation and long dry periods. The analyses are based on a collation of high‐resolution rain‐gauge data from seven Alpine countries, with 5500 measurements per day on average, spanning the period 1971–2008. The dataset is an update of an earlier version with improved data density and more thorough quality control. The grid dataset has a grid spacing of 5 km, daily time resolution, and was constructed with a distance‐angular weighting scheme that integrates climatological precipitation–topography relationships. Scales effectively resolved in the dataset are coarser than the grid spacing and vary in time and space, depending on station density. We quantify the uncertainty of the dataset by cross‐validation and in relation to topographic complexity, data density and season. Results indicate that grid point estimates are systematically underestimated (overestimated) at large (small) precipitation intensities, when they are interpreted as point estimates. Our climatological analyses highlight interesting variations in indicators of daily precipitation that deviate from the pattern and course of mean precipitation and illustrate the complex role of topography. The daily Alpine precipitation grid dataset was developed as part of the EU funded EURO4M project and is freely available for scientific use.

Effects of climate change on mass movements in mountain environments

Changes in temperature and precipitation have a range of impacts, including change of glacier extent, extent and duration of snow cover, and distribution and thermal properties of permafrost. Similarly, it is likely that climatic changes affect frequency and magnitude of mass movements, such as shallow landslides, debris flows, rock slope failures, or ice avalanches. However, so far changes in mass-movement activity can hardly be detected in observational records. In this progress report we document the role of climate variability and change on mass-movement processes in mountains through the description and analysis of selected, recent mass movements where effects of global warming and the occurrence of heavy precipitation are thought to have contributed to, or triggered, events. In addition, we assess possible effects of future climatic changes on the incidence of mass-movement processes. The report concentrates on high-mountain systems, including processes such as glacier downwasting and the formation of new ice-marginal lakes, glacier debuttressing and the occurrence of rock slope instability, temperature increase and permafrost degradation, as well as on changing sediment reservoirs and sediment supply, with a clear focus on studies from the European Alps.