Evolution Of Rainfall Research Articles

On the sensitivity of seasonal and diurnal precipitation to cumulus parameterization over CORDEX-EA-II

The ability of the Weather Research and Forecasting (WRF) model in simulating the seasonal and diurnal cycles of rainfall over the Coordinated Regional Climate Downscaling Experiment East Asia Phase II (CORDEX-EA-II) domain is validated against the Tropical Rainfall Measuring Mission (TRMM) datasets. A focus is placed on the role of convective parameterization (CP) schemes. A set of numerical experiments at a 25 km resolution for 1998–2009, using six different CPs, is performed to evaluate the physics-dependency of simulation results. All CPs simulate realistic summer mean precipitation and its northward propagation, with the best performance in the Simplified Arakawa-Schubert (SAS). The biases in the seasonal evolution of rainfall are related to the deficiency in simulated low-level winds and the northward propagation of the cyclonic vorticity. The simulated earlier peak time in other CPs is delayed by about 1–2 h by the Kain-Fritsch with a modified trigger function (KFMT), although this scheme shows a disadvantage in the magnitude. The performance of different CPs in simulating diurnal rainfall cycles is dependent on regions, and none of them performs better than the others for all the sub-regions. The initiation of simulated convection is weakly physics-dependent. However, the timing and magnitude of stratiform precipitation differ among the six experiments. A further analysis shows that the dry biases over the lower Yangtze River basin are a result of the weakened southwesterly water vapor transport, while the excessive afternoon rainfall in the Kain-Fritsch (KF) simulation is attributed to the largest positive perturbation in the lower level atmosphere, especially the enhanced vertical transport of humidity.

Differences in the Rainfall Characteristics between Mount Tai and Its Surrounding Areas

As a typical small-scale, isolated topography, Mount Tai exhibits great differences in precipitation characteristics from the surrounding areas. It was found that the amount of rainfall occurring over Mount Tai is significantly larger than what is observed in the surrounding areas. Based on hourly rain gauge records for the warm season (May to September) of 1996–2015, differences between Mount Tai and its surrounding areas were further revealed in terms of rainfall diurnal variation, spatial scale, and evolution process. The diurnal variation of the enhancement on rainfall amount exhibit “dual peaks” occurring in the early morning and afternoon, and the dual peaks are mainly attributable to rainfall frequency. The diurnal phase of the rainfall amount in the surrounding areas lags 1 h behind that over Mount Tai. Regarding differences in rainfall spatial scale, compared to those of surrounding areas, precipitation over Mount Tai is characterized by a smaller coverage, especially in the early morning. Mount Tai also tends to have a kind of unique, small-scale rainfall in the afternoon and at night. Based on statistical analysis of precipitation events, differences in rainfall evolution process were identified as well. Rainfall over Mount Tai often starts earlier in the afternoon and ends later at night than it does in the surrounding areas. Furthermore, nocturnal rainfall events over Mount Tai are prone to peaking over a shorter period and enduring for a longer period after reaching their maximum intensity, compared with nocturnal rainfall events occurring in the surrounding areas. Rainfall events over Mount Tai always last longer, especially those occurring in the early morning. In general, Mount Tai has a large enhancement effect on rainfall.

Using nowcasting technique and data assimilation in a meteorological model to improve very short range hydrological forecasts

Abstract. Forecasting flash floods some hours in advance is still a challenge, especially in environments made up of many small catchments. Hydrometeorological forecasting systems generally allow for predicting the possibility of having very intense rainfall events on quite large areas with good performances, even with 12–24 h of anticipation. However, they are not able to predict the exact rainfall location if we consider portions of a territory of 10 to 1000 km2 as the order of magnitude. The scope of this work is to exploit both observations and modelling sources to improve the discharge prediction in small catchments with a lead time of 2–8 h. The models used to achieve the goal are essentially (i) a probabilistic rainfall nowcasting model able to extrapolate the rainfall evolution from observations, (ii) a non-hydrostatic high-resolution numerical weather prediction (NWP) model and (iii) a distributed hydrological model able to provide a streamflow prediction in each pixel of the studied domain. These tools are used, together with radar observations, in a synergistic way, exploiting the information of each element in order to complement each other. For this purpose observations are used in a frequently updated data assimilation framework to drive the NWP system, whose output is in turn used to improve the information as input to the nowcasting technique in terms of a predicted rainfall volume trend; finally nowcasting and NWP outputs are blended, generating an ensemble of rainfall scenarios used to feed the hydrological model and produce a prediction in terms of streamflow. The flood prediction system is applied to three major events that occurred in the Liguria region (Italy) first to produce a standard analysis on predefined basin control sections and then using a distributed approach that exploits the capabilities of the employed hydrological model. The results obtained for these three analysed events show that the use of the present approach is promising. Even if not in all the cases, the blending technique clearly enhances the prediction capacity of the hydrological nowcasting chain with respect to the use of input coming only from the nowcasting technique; moreover, a worsening of the performance is observed less, and it is nevertheless ascribable to the critical transition between the nowcasting and the NWP model rainfall field.

Variability of monsoon low‐level jet and associated rainfall over India

AbstractThe structure and climatology of the monsoon low‐level jet (MLLJ) is studied based on dynamically downscaled simulations over a 37‐year period (1980–2016) using the Weather Research Forecasting (WRF) model. The simulations are conducted by adopting a continuous initialization method with daily re‐initializations using ERA‐Interim data as initial and boundary conditions. Validation of the downscaled fields with radiosonde data shows that the model has reasonable skill in reproducing MLLJ characteristics. Analysis of the simulations suggests that the MLLJ exhibits systematic diurnal variation: maximum winds of the synoptically induced large‐scale monsoon jet occur during the daytime, and the orographic channelled winds through the mountains of East Africa, Hejaz, and Western Ghats in the night‐time. These diurnal changes in monsoon winds modulate the moisture convergence process and the associated evolution of rainfall over India. Seasonal and monthly climatology of monsoon winds shows that the model accurately reproduces the spatial pattern of winds and slightly overestimates (2–3 m/s) the mean monthly winds over the Bay of Bengal and Arabian Seas. Analysis of wind variability and the trends using 37 years simulations suggests that the MLLJ exhibits an increasing trend in wind speed on both seasonal and monthly scales, except for August which shows a decreasing trend. The weakening of the MLLJ in August has a profound influence on the number of monsoon depressions forming over the Bay of Bengal (which are decreasing), and on the number of break days (which are increasing) and associated precipitation reduction over the central Indian region.

Spatial and Temporal Variability in Precipitation Concentration over Mainland China, 1961–2017

Understanding the patterns and mechanisms of precipitation variations is important for assessing flood and drought risks and for ensuring sustainable water use. Here, we analyzed the characteristics of annual precipitation changes in eight subregions of China using the Mann–Kendall test based on daily precipitation data from 774 rain gauge stations during 1961–2017. Then, we used the monthly precipitation concentration index (PCI) and daily concentration index (CI) to analyze precipitation concentrations. The results are as follows: (1) PCI and CI in northern China generally decreased with time, indicating a uniform precipitation distribution. Notably, the annual precipitation increased significantly in Xinjiang and the Qinghai-Tibet Plateau, which could alleviate future drought. (2) PCI increased and CI decreased in the plain regions of the Yangtze River and Southeast China, exhibiting high CI values with marked increases of annual precipitation. Such heavy rainfall events combined with high rainfall concentrations could increase the flood risk. (3) A significant PCI increase and CI decrease occurred in Southwest China, where annual precipitation decreased significantly. Regular rainfall decreased notably, which could increase the likelihood of drought hazards. (4) Overall, both indices showed negative trends at most stations; precipitation distribution was generally more uniform over China. These findings improve our understanding of extreme rainfall evolution and water resource distribution over China. Furthermore, PCI and CI can serve as warning tools for disaster control and water resource management.

Impacts of Rainfall and Temperatures on Socioeconomic and Environmental Sectors in the Communes of Tondikiwindi and Ouallam, Department of Ouallam, Region of Tillaberi, Niger Republic

The communes of Tondikiwindi and Ouallam in Niger experience changes in rainfall and temperatures like the whole of ahel. This paper focuses on understanding the impacts of these climate parameters on socio-economic and environmental sectors. The methodology is based on calculations of various indices (Lamb, 1982; Tabony, 1977; FAO / UNESCO, 1979) and determination of temperatures within maxima and minima values. With regard to the rainfall evolution, three periods were noted including a long dry period (1968-1989), a relatively wet period (1990-1998), and a period of great variability with an alternation of wet and dry years (1999 -2015). A trend in the South has been noticed in the start and at the end of the rainy season, with a slight decrease in the rainy days. For the temperatures, an increase was registered from 1968 up to date with some slight changes. This is due to the occurrence of the phenomena related to the El Nino or ENSO Southern Oscillation. In terms of impacts, there were several food crises and population migration both inside and outside of the country. On the other hand, the return to a relatively humid phase has led to a change in the Northern limit of cultures, whose corollary is the exacerbation of conflicts between shared natural resources users. This return to an increase in rainfall has also led to major floods that have favored the creation of new permanent or semipermanent pools. Hence, it is necessary to develop a new model of sustainable development for this geographical entity.

The role of aerosols and greenhouse gases in Sahel drought and recovery

We exploit the multi-model ensemble produced by phase 5 of the Coupled Model Intercomparison Project (CMIP5) to synthesize current understanding of external forcing of Sahel rainfall change, past and future, through the lens of oceanic influence. The CMIP5 multi-model mean simulates the twentieth century evolution of Sahel rainfall, including the mid-century decline toward the driest years in the early 1980s and the partial recovery since. We exploit a physical argument linking anthropogenic emissions to the change in the temperature of the sub-tropical North Atlantic Ocean relative to the global tropical oceans to demonstrate indirect attribution of late twentieth century Sahel drought to the unique combination of aerosols and greenhouse gases that characterized the post-World War II period. The subsequent reduction in aerosol emissions around the North Atlantic that resulted from environmental legislation to curb acid rain, occurring as global tropical warming continued unabated, is consistent with the current partial recovery and with projections of future wetting. Singular Value Decomposition (SVD) applied to the above-mentioned sea surface temperature (SST) indices provides a succinct description of oceanic influence on Sahel rainfall and reveals the near-orthogonality in the influence of emissions between twentieth and twenty-first centuries: the independent effects of aerosols and greenhouse gases project on the difference of SST indices and explain past variation, while the dominance of greenhouse gases projects on their sum and explains future projection. This result challenges the assumption that because anthropogenic warming had a hand in past Sahel drought, continued warming will result in further drying. In fact, the twenty-first century dominance of greenhouse gases, unchallenged by aerosols, results in projections consistent with warming-induced strengthening of the monsoon, a response that has gained in coherence in CMIP5 compared to prior multi-model exercises.

English

The rainfall disturbances observed in the recent decades in Cote d'Ivoire constitute a constraint for sustainable cocoa production, the mainstay of the Ivorian economy. These disturbances constitute, in addition to the losses of production and those from the quality of the cocoa beans, one of the causes of the high cocoa mortality at the recovery stage in all cocoa production area. The present study, carried out in the Goh and Loh Djiboua, post-pioneer regions, is a contribution for the searching of solutions to the continuity challenge of the Ivorian cocoa farming in front of the climate change. It aims to analyze not only the evolution and distribution of rainfall, but also to identify the rainfall constraints related to cocoa farming, and to propose possible solutions to ensure the sustainability of cocoa farming in these two regions. The analysis covered the three decades of the period from 1986 to 2015. The rainfall data were collected at the weather stations of the CNRA (Centre National de Recherche Agronomique) based both on Divo and Gagnoa. The study of the two rainfall data series using the rainfall index showed that the current climate of the two regions is characterized by a predominance of dry periods at Divo and the wet one in Gagnoa. Also, 40 to 90% of the 30-years recorded less than 700 mm of rain during the main rainy season both in the two regions. In addition the beginning of the rainy season in the two regions is between the 1st and 2nd 10 days of March in both regions, while in practice the planting of cacao is usually made in May or June. To note this variability, the technical itineraries for all regions must to be regionalized to enable cocoa to exhibit its potentialities in its new production environment. Key words: Rainfall assessment, Loh-Djiboua and Goh regions, sustainable cocoa farming.

Circulation structures leading to propagating and non-propagating heavy summer rainfall in central North China

Using 30 years of hourly rain gauge records and reanalysis data, this paper reveals two types of heavy summer rainfall in central North China (CNC): the lasting mountain (LM) rainfall and the mountain–plain (MP) rainfall, and further explains their formation mechanisms. The evolutions of the rainfall are found to be closely connected to upper-tropospheric temperature anomalies. When upper-tropospheric warm (cold) anomalies dominate North China (the Japan Sea) and stretch down to lower layers, positive (negative) geopotential anomalies, which appear above the warm (cold) anomalies governed by hydrostatic equilibrium, extend from upper to lower troposphere. In the lower layers, evident low-level easterly anomalies form to the south (north) of the positive (negative) geopotential center, controlling the downstream of CNC and making convective systems difficult to progress eastward. Correspondingly, the low-level convergence and strong convection maintain in the west, and the rainfall persists over the mountains constituting the LM process. But when upper-tropospheric cold (warm) anomalies dominate the west (east) of 110°E and stretch down to lower layers, CNC is situated between an upstream trough and a downstream ridge. As the trough-ridge system progresses eastward, the low-level moisture tongue and strong convections in front of the trough move from the mountains to the plains, and the rainfall propagates downstream constituting the MP process. Results in this paper indicate that upper-tropospheric temperature has significant influence on the evolution of rainfall, and pay attention to its characteristics could provide helpful information in the analysis and forecasting of rainfall propagation.

The climate changes in the sub-basin of the Oum Er rbia central and the impact on the surface waters.

Observations and model results indicate that climate trends in North Africa show both drying and warming over the past few decades, according to the latest Intergovernmental Panel on Climate Change (IPCC) assessment. During the last decades, due to changes in climatic and environmental conditions, water resources available in Morocco are decreasing. They are, moreover, subject to extreme cyclical variations and to soaring water demands because of rapid population growth, improvement of living standards, industrial development and expansion of irrigated agriculture. The pressure on these water resources is accompanied by a growing and increasingly serious degradation of their quality. This is found at the level of average of air temperatures that are continuously growing and at the level of precipitation with an average potential of water in the area with a significant decrease in the last forty years. The purpose of this work is to make a study on the impact of climate change on water resources that exist in the basin of the Oum Er Rbia Central, and to give justifiable results regarding the evolution of climate change over time. From the created database, we brought out diagrams, curves and maps of the evolution of climate change that show the results below: The study of the evolution of rainfall recorded since 1934 and the breaks in time series highlighted two methodologically distinct periods: a wet period with high rainfall (1986 - 1971), a dry season and low rainfall (1970/71 to 2007). Observed climatic trends, calculated over the period of 1935-2007 and reported in the study, indicate the following: On an annual basis, changes in precipitation were not significant and varied from one region to another. On the other hand, spring rainfall declined significantly in the northern part of Morocco at a rate of 0.5 mm / day per decade; That the area experienced an average annual rainfall reduction of 70 mm (20%) over this period compared to 1940-1980. The area is a hydraulic region that is already experiencing a water deficit. The sharp decline in water supplies since 1980-2007 (by 40% compared with 1940- 1980) and the increase in demand and water degradation by different causes; The annual average flows measured at the the central Oum Er Rbia stations were reduced by considerable hydrological deficits ranging between 40.8 and 49.5%. Global warming and rainfall regression are added to the intrinsic conditions of sub basins of the Oum Er Rbia Central (especially waterproofing of land and the lack of groundwater reservoir) to increase its vulnerability to water scarcity. This critical situation requires adapting good management methods of meteorological water as the only source of water in this basin.You should leave 8 mm of space above the abstract and 10 mm after the abstract. The heading Abstract should be typed in bold 9- point Arial. The body of the abstract should be typed in normal 9-point Times in a single paragraph, immediately following the heading. The text should be set to 1 line spacing. The abstract should be centred across the page, indented 17 mm from the left and right page margins and justified. It should not normally exceed 200 words.

Modeling Process Chain of Meteorological Reanalysis Precipitation Data Using Work Context

In this paper, we propose a models of process chain and knowledge-based of meteorological reanalysis datasets that help scientists, working in the field of climate and in particular of the rainfall evolution, to solve uncertainty of spatial resources (data, process) to monitor the rainfall evolution. Indeed, rainfall evolution mobilizes all research, various methods of meteorological reanalysis datasets processing are proposed. Meteorological reanalysis datasets available, at present, are voluminous and heterogeneous in terms of source, spatial and temporal resolutions. The use of these meteorological reanalysis datasets may solve uncertainty of data. In addition, phenomena such as rainfall evolution require the analysis of time series of meteorological reanalysis datasets and the development of automated and reusable processing chains for monitoring rainfall evolution. We propose to formalize these processing chains from modeling an abstract and concrete models based on existing standards in terms of interoperability. These processing chains modelled will be capitalized, and diffusible in operational environments. Our modeling approach uses Work-Context concepts. These concepts need organization of human resources, data, and process in order to establish a knowledge-based connecting the two latter. This knowledge based will be used to solve uncertainty of meteorological reanalysis datasets resources for monitoring rainfall evolution.

MODELING PROCESS CHAIN OF METEOROLOGICAL REANALYSIS PRECIPITATION DATA USING WORK CONTEXT

In this paper, we propose a models of process chain and knowledge-based of meteorological reanalysis datasets that help scientists, working in the field of climate and in particular of the rainfall evolution, to solve uncertainty of spatial resources (data, process) to monitor the rainfall evolution. Indeed, rainfall evolution mobilizes all research, various methods of meteorological reanalysis datasets processing are proposed. Meteorological reanalysis datasets available, at present, are voluminous and heterogeneous in terms of source, spatial and temporal resolutions. The use of these meteorological reanalysis datasets may solve uncertainty of data. In addition, phenomena such as rainfall evolution require the analysis of time series of meteorological reanalysis datasets and the development of automated and reusable processing chains for monitoring rainfall evolution. We propose to formalize these processing chains from modeling an abstract and concrete models based on existing standards in terms of interoperability. These processing chains modelled will be capitalized, and diffusible in operational environments. Our modeling approach uses Work-Context concepts. These concepts need organization of human resources, data, and process in order to establish a knowledge-based connecting the two latter. This knowledge based will be used to solve uncertainty of meteorological reanalysis datasets resources for monitoring rainfall evolution.

A Conceptual Model for the Response of Tropical Rainfall to Orbital Variations

Abstract Tropical rainfall to first order responds to variations in Earth’s orbit through shifts of the intertropical convergence zone (ITCZ) and changes in zonally averaged rainfall intensity. Here, a conceptual model is developed that represents both processes and their response to orbital insolation variations. The model predicts the seasonal evolution of tropical rainfall between 30°S and 30°N. Insolation variations impact seasonal rainfall in two different ways: thermodynamically, leading to variations in rainfall intensity through modulation of the water vapor content of the atmosphere; and dynamically, leading to shifts of the ITCZ through modulation of the global atmospheric energy budget. Thermodynamic and dynamic effects act together to shape the annual-mean response of tropical rainfall to changes in Earth’s orbit. The model successfully reproduces changes in annual-mean rainfall inferred from paleo-proxies across several glacial–interglacial cycles. It illuminates how orbital precession and variations of Earth’s obliquity affect tropical rainfall in distinct ways near the equator and farther away from it, with spectral signatures of precession and obliquity variations that shift with latitude. It also provides explanations for the observed different phasings of rainfall minima and maxima near the equator and away from it. For example, the model reproduces a phase shift of ~10 ka between rainfall records from caves in northern Borneo (4°N) and from China (approximately 30°N). The model suggests that such phase shifts arise through a different weighting of ITCZ shifts and variations in rainfall intensity, thus providing insight into the mechanisms that drive tropical rainfall changes on orbital time scales.

Internally Generated and Externally Forced Multidecadal Oceanic Modes and Their Influence on the Summer Rainfall over East Asia

Abstract Interdecadal oceanic variabilities can be generated from both internal and external processes, and these variabilities can significantly modulate climate on global and regional scales, including the warming slowdown in the early twenty-first century and rainfall in East Asia. By analyzing simulations from a unique Community Earth System Model (CESM) Large Ensemble (CESM-LE) project, it is shown that the interdecadal Pacific oscillation (IPO) is primarily an internally generated oceanic variability, while the Atlantic multidecadal oscillation (AMO) may be an oceanic variability generated by internal oceanic processes and modulated by external forcing in the twentieth century. Although the observed relationship between IPO and the Yangtze–Huaihe River valley (YHRV) summer rainfall in China is well simulated in both the preindustrial control and the twentieth-century ensemble simulation, none of the twentieth-century ensemble members can reproduce the observed time evolution of both the IPO and YHRV rainfall because of the unpredictable nature of IPO on multidecadal time scales. On the other hand, although CESM-LE cannot reproduce the observed relationship between the AMO and Huanghe River valley (HRV) summer rainfall of China in the preindustrial control simulation, this relationship in the twentieth-century simulations is well reproduced, and the chance of reproducing the observed time evolution of both AMO and HRV rainfall is about 30%, indicating the important role of the interaction between the internal processes and the external forcing to realistically simulate the AMO and HRV rainfall.

Typhoon Nina and the August 1975 Flood over Central China

Abstract The August 1975 flood in central China was one of the most destructive floods in history. Catastrophic flooding was the product of extreme rainfall from Typhoon Nina over a 3-day period from 5 to 7 August 1975. Despite the prominence of the August 1975 flood, relatively little is known about the evolution of rainfall responsible for the flood. Details of extreme rainfall and flooding for the August 1975 event in central China are examined based on empirical analyses of rainfall and streamflow measurements and based on downscaling simulations using the Weather Research and Forecasting (WRF) Model, driven by Twentieth Century Reanalysis (20CR) fields. Key hydrometeorological features of the flood event are placed in a climatological context through hydroclimatological analyses of 20CR fields. Results point to the complex evolution of rainfall over the 3-day period with distinctive periods of storm structure controlling rainfall distribution in the flood region. Blocking plays a central role in controlling anomalous storm motion of Typhoon Nina and extreme duration of heavy rainfall. Interaction of Typhoon Nina with a second tropical depression played a central role in creating a zone of anomalously large water vapor transport, a central feature of heavy rainfall during the critical storm period on 7 August. Analyses based on the quasigeostrophic omega equation identified the predominant role of warm air advection for synoptic-scale vertical motion. Back-trajectory analyses using a Lagrangian parcel tracking algorithm are used to assess and quantify water vapor transport for the flood. The analytical framework developed in this study is designed to improve hydrometeorological approaches for flood-control design.

SIMULATION OF TROPICAL CYCLONE 201610 (LIONROCK) AND ITS REMOTE EFFECT ON HEAVY RAINFALL IN HOKKAIDO

When tropical cyclone (TC) 201610, namely Lionrock, was moving over the western North Pacific from southeast of Honshu to cut across the Tohoku region during 29-30 August 2016, continuous and intense rainfall occurred in mid- to southeastern Hokkaido, far from the TC center. The Weather Research and Forecast (WRF) model is used to investigate the possible remote effect of TC Lionrock on this heavy rain in Hokkaido. The National Center for Environmental Prediction (NCEP) global final (FNL) analysis is used to provide both the initial and lateral boundary conditions for the model. Three numerical experiments are performed. In the control experiment (CTL), the original FNL is used. In the no-TC experiment (NoTC), the vortex associated with TC Lionrock in the FNL is removed such that the TC signal does not appear at the initial time. In the no-topography experiment (noTopo), the terrain height over Hokkaido set to 1 m if it is higher than 1 m. As verified against observations, the CTL and noTopo experiments capture reasonably well the TC track. The CTL experiment also reproduces relatively well the spatial distribution and temporal evolution of rainfall, whereas the remote rainfall in Hokkaido is largely suppressed in the noTC experiment, suggesting a significant far-reaching effect of TC Lionrock. The combined effect of Lionrock and the stationary low-pressure system located over the Sea of Japan enhances the moisture transport towards Hokkaido through their outer circulation. Particularly, only very small amount of rainfall is observed in Hokkaido in the noTopo experiment, indicating that the orographic forcing of the southeastern mountains in Hokkaido plays the most critical role in this extreme rainfall event.

Rainfall Variability and Trend Analysis of Annual Rainfall in North Africa

The IPCC climate models predict, for the Maghreb countries, lower rainfall and increased aridity. Current observations in the three countries of central Maghreb (Morocco, Algeria, and Tunisia) are not consistent with these predictions. To demonstrate this new trend, a detailed regional analysis of rainfall evolution is conducted. This investigation is based on the calculation of the reduced centered index and the chronological graphical method of processing information (MGCTI) of “Bertin matrix” type. The results show extreme variability of this parameter and the severe past drought (more intense for Morocco, in which the drastic conditions from the seventies are observed). The results also show the beginning of a gradual return to wetter conditions since the early 2000s in Algeria and Tunisia and from 2008 for Morocco (this trend is confirmed by recent agricultural production data in 2011/2012 and 2012/2013).

Slow Preconditioning for the Abrupt Convective Jump over the Northwest Pacific during Summer

Abstract The rapid intensification of convective activity in mid-July over the northwest Pacific marks the final stage of the Asian summer monsoon, accompanied by major shifts in regional rainfall and circulation patterns. An entraining plume model is used to investigate the physical processes underlying the abrupt convective jump. Despite little change in sea surface temperature (SST), gradual lower-troposphere mixing leads to a threshold transition in the model as follows. Before mid-July, although SST is already high (29°C), the convective plume is inhibited by the capping inversion above the trade cumulus boundary layer. As the lower troposphere is gradually mixed, the boundary layer top rises with reduced atmospheric stability and increased humidity in the lower troposphere. These factors weaken the inhibition effect of the inversion on the entraining plume. As soon as the plume is able to overcome the inversion barrier, it can rise all the way to the upper troposphere. This marks an abrupt threshold transition to a deep convection regime with heavy rainfall. The convective available potential energy (CAPE) of the entraining plume is found to be a better indicator of the rainfall intensity compared to the conventional undiluted CAPE. The latter fails to capture the onset by neglecting interactions between convective clouds and the environment. Current general circulation models (GCMs) fail to capture the abrupt convective jump and instead simulate a rather smooth seasonal evolution of rainfall. Compared to observations, GCMs simulate a higher trade cumulus top with excessive mixing in the lower troposphere. Convection is no longer inhibited by the inversion barrier, and rainfall simply follows the smooth variation of SST.

Évolution Des Extrêmes Pluviométriques Dans La Région Du Gôh (Centre-Ouest De La Côte d’Ivoire)

The Gôh region located in western-central Ivory Coast is a region whose economy depends mainly on agriculture, which itself is dependent on the climate. Thus, variation and climate change has a significant impact on crop yields. The objective of this work is to study the evolution of extreme rainfall on rainfall station in the region (Gagnoa station). The calculation of rainfall indices was performed with the software RclimDex. It appears from this study has the Gagnoa station, five (5) of the seven indices calculated namely, the maximum rainfall of one day height (Rx1day), the maximum total rainfall of 5 days (Rx5daiy), the days very rainy (R95) extremely rainy days (R99p) and consecutive dry days (CDD) experienced an increase. While the total annual rainfall (PRCPTOT) and consecutive wet days (CWD) declined. In general, the GOH region is experiencing a decline in rainfall and therefore an increase in dry spells during the rainy seasons.

EVOLUÇÃO TEMPORAL DA PRECIPITAÇÃO E ATIVIDADE ELÉTRICA DE UMA TEMPESTADE COM OCORRÊNCIA DE TEMPO SEVERO

This study aimed to analyze the spatial and temporal evolution of rainfall and electrification of a Convective System, which occured on March 12, 2012 over the city of São Paulo, during the time interval from 1830 to 1945 UTC. An analysis was made of the behavior of the three dimensional structure of radar reflectivity and lightning type Intra-cloud (IN) and Cloud-Solo (NS), based on two lightning detection networks installed in the region during the RAIN Project, in order to correlate the occurrence of severe weather to the evolution of cloud ascending current, precipitation formation and electrification of this storm. It was observed by the reflectivity of the FCTH Radar images that, at times, the SC showed high values of reflectivity, with over 70 dBZ and indicating the presence of hail within the system. Through the behavior of electrical discharges, it is also noted that these accompany the displacement and intensity of the updraft and through the lightning jump, it is possible to detect in advance whether if the storm is intensifying or not. If so, this storm could possibly become a severe weather and cause serious damage to society.