convection permitting simulation

A novel convection permitting modelling framework that combines a pseudo‐global warming approach with continuously forced deep soil moisture from prescribed perturbation storylines is applied in the Eastern European Alpine region and parts of the Pannonian Basin to investigate soil moisture precipitation (SMP) feedbacks on summertime precipitation and the feedbacks’ role under changed climate conditions. A set of 1‐year convection‐permitting (3 km horizontal grid spacing) soil moisture sensitivity simulations with the regional climate model of the Consortium for Small‐Scale Modelling in Climate Mode are conducted. In order to account for global warming, end‐of‐the‐century climate change effects from four global climate models, projecting the greenhouse gas concentration scenario RCP 8.5, are imprinted. The simulations reveal that (1) the locations of precipitation events are highly sensitive to soil moisture modifications while intensities and the internal structure of precipitation...

A novel convection permitting modelling framework that combines a pseudoglobal warming approach with continuously forced deep soil moisture from prescribed perturbation storylines is applied in the Eastern European Alpine region and parts of the Pannonian Basin to investigate soil moisture precipitation (SMP) feedbacks on summertime precipitation and the feedbacks' role under changed climate conditions. A set of 1-year convection-permitting (3 km horizontal grid spacing) soil moisture sensitivity simulations with the regional climate model of the Consortium for Small-Scale Modelling in Climate Mode are conducted. In order to account for global warming, end-of-the-century climate change effects from four global climate models, projecting the greenhouse gas concentration scenario RCP 8.5, are imprinted. The simulations

Extremely heavy rainfall has been occurred over Kerala, southwest coast of India, during mid-August 2018. The meteorological conditions during this period are analysed, and it is found that a combination of many rain favouring conditions prevailed at that time. The positive phase of Madden Julian Oscillation coupled with a monsoon depression in the Bay of Bengal and a weak trough in the south-eastern Arabian Sea strengthened the Monsoon Low Level Jet bringing moisture-laden winds over Kerala. The rising limb of Walker and Hadley circulations was also found over Kerala, which gave favourable updraft for cloud formation. In addition, the core of the Tropical Easterly Jet was found over the Kerala and Karnataka region. The cyclonic circulation in the mid-troposphere observed around the monsoon depression extended up to the west coast of India. Simultaneous occurrences of all these could have contributed to the extreme rainfall events and severe floods over Kerala.

Extremely heavy rainfall has been occurred over Kerala, southwest coast of India, during mid-August 2018. The meteorological conditions during this period are analysed, and it is found that a combination of many rain favouring conditions prevailed at that time. The positive phase of Madden Julian Oscillation coupled with a monsoon depression in the Bay of Bengal and a weak trough in the south-eastern Arabian Sea strengthened the Monsoon Low Level Jet bringing moisture-laden winds over Kerala. The rising limb of Walker and Hadley circulations was also found over Kerala, which gave favourable updraft for cloud formation. In addition, the core of the Tropical Easterly Jet was found over the Kerala and Karnataka region. The cyclonic circulation in the mid-troposphere observed around the monsoon depression extended up to the west coast of India. Simultaneous occurrences of all these could have contributed to the extreme rainfall events and severe floods over Kerala.

Global climate models including the Climate Forecast System version 2, the operational model used for prediction of Indian summer monsoon rainfall by the India Meteorological Department, has dry precipitation bias, mostly over densely populated Ganga basin. This restricts the use of model output in hydrological simulations/forecasts. We use regional atmospheric Weather Research and Forecasting model coupled with land surface models, driven by the boundary conditions from Climate Forecast System version 2. We find significant reduction in the dry bias of Indian summer monsoon rainfall with regional land-atmosphere model and this attributes to (a) improved moisture transport from Western and Upper Indian Ocean to Ganga Basin and (b) improved precipitation recycling over the Ganga basin. We find that the smoothened topography in the global model allows advection of cold dry subtropical air into the Indian monsoon region, contributing to the cold temperature and dry precipitation bias. These results have important implications for monsoon simulations in developing operational hydroclimatic prediction system in India. Plain Language Summary The operational monsoon prediction model for India, Climate Forecast System version 2, has significant dry bias in precipitation over the Ganga basin, and this restricts the use of model output for hydrologic prediction. We attribute such bias to the lack of representation of land surface processes and characteristics in the model. We show that an improved representation of land characteristics in a regional coupled atmospheric-land model improves not only the land-atmosphere interactions but also the moisture contributions from distant oceanic sources. This finally results into improved simulations of monsoon.

The regional climate of the Arabian Gulf region is modeled using a set of simulations based on the Weather Research and Forecasting (WRF) Model, including a 30-yr benchmark simulation driven by reanalysis data, and two bias-corrected Community Earth System Model (CESM)-driven (BCD) WRF simulations for retrospective and future periods that both include 10-yr convection-permitting nested simulations. The modeled precipitation is cross-validated using Tropical Rainfall Measuring Mission data, rain gauge data, and the baseline dataset from the benchmark simulation. The changes in near-surface temperature, precipitation, and ambient conditions are investigated using the BCD WRF simulations. The results show that the BCD WRF simulation well captures the precipitation distribution, the precipitation variability, and the thermodynamic properties. In a warmer climate under the RCP8.5 scenario around the year 2070, the near-surface temperature warms by ~3°C. Precipitation increases over the A...

Probable maximum precipitation (PMP), defined as the largest rainfall depth that could physically occur under a series of adverse atmospheric conditions, has been an important design criterion for critical infrastructures such as dams and nuclear power plants. To understand how PMP may respond to projected future climate forcings, we used a physics-based numerical weather simulation model to estimate PMP across various durations and areas over the Alabama-Coosa-Tallapoosa (ACT) River Basin in the southeastern United States. Six sets of Weather Research and Forecasting (WRF) model experiments driven by both reanalysis and global climate model projections, with a total of 120 storms, were conducted. The depth-area-duration relationship was derived for each set of WRF simulations and compared with the conventional PMP estimates. Our results showed that PMP driven by projected future climate forcings is higher than 1981-2010 baseline values by around 20% in the 2021-2050 near-future and 44% in the 2071-2100 far-future periods. The additional sensitivity simulations of background air temperature warming also showed an enhancement of PMP, suggesting that atmospheric warming could be one important factor controlling the increase in PMP. In light of the projected increase in precipitation extremes under a warming environment, the reasonableness and role of PMP deserve more in-depth examination. 1. Introduction Probable maximum precipitation (PMP) is defined as "the greatest depth of precipitation for a given duration meteorologically possible for a design watershed or a given storm area at a particular location at a particular time of year" [World Meteorological Organization, 2009], and it represents the largest rainfall that could physically occur under a series of adverse atmospheric conditions [

Soil moisture can play an important role for determining precipitation characteristics over the tropical Asian region. In this study with the help of convection-permitting regional climate model (RCM), impacts of soil moisture on precipitation characteristics are investigated on different temporal scales over the Indian monsoon region. A set of wet and dry soil moisture surface conditions were forced to the Weather Research and Forecasting model WRFv3.9.1.1 as the RCM during the summer monsoon season. The contrasting soil moisture conditions found to affect the timing, frequency, intensity, and duration of precipitation during the peak monsoon over central India, along the mountains of foothills of Himalayas and over the Bay of Bengal. To understand diurnal contribution to daily accumulated rainfall, we also analyzed diurnal variations of precipitation characteristics. The changes in precipitation characteristics due to the surface conditions are basically regional characteristics. During noon/afternoon, a greater frequency of convective precipitation over the Indian land region, along the mountains of western Ghats and foothills of Himalayas was simulated under the wet surface condition, compared with the dry surface condition. Weakening of convective precipitation was found associated with the wetter surface conditions over the Indian land region. The frequency of short duration (3-6 hours) rainfall events were found to increase over Indian land region under the wet surface conditions than dry. In addition, the frequency of mesoscale convective systems propagating from land to the offshore Bay of Bengal found to decrease during the early morning over the wet land surface condition, compared with the dry condition. Moreover, we will discuss the mechanisms why these changes are simulated. Convection-permitting simulation, impact of land surface condition, Indian summer monsoon, precipitation characteristics AAS10-P15 JpGU-AGU Joint Meeting 2020

xx Precipitation during the Indian summer monsoon exhibits diurnal, intra-seasonal, and inter-annual variabilities. Among these variabilities, the diurnal convection cycle is the fundamental variability mode for tropical climates. In terms of the summer monsoon, this diurnal cycle of convection is an essential trigger that develops and organizes precipitation systems and contributes to the spatial and temporal distribution of monsoonal precipitation. The developmental features of these diurnal convection and precipitation systems are not well represented in global and regional climate models across different monsoon regions. Such uncertainty in the diurnal convection representation undermines the fundamental reliability of the simulated physical processes in the climate models. This has encouraged an examination into the unpredictability of the Indian monsoon diurnal convection in climate models; this has received little research attention in the past. Current research has focused on observations and modeling techniques to diagnose the observed diurnal convection cycle in a tropical monsoon and understand the importance of its representation in climate models. After simulating the diurnal cycle realistically in the regional climate model, we explored the sensitivity of diurnal precipitation characteristics to Indian land surface conditions over heterogeneous surfaces. This study begins with an observational understanding of the diurnal convection cycle in terms of precipitation and its characteristics during the summer monsoon. This is carried out using satellite observations from the 21-y (1998 2018) climatology of the Tropical Rainfall Measurement Mission (TRMM) 3B42 V7 dataset. The diurnal cycle

For the Asian summer monsoon, diurnal cycle of convection is an essential trigger that develops and organizes precipitation systems and contributes to the spatial and temporal distribution of monsoonal precipitation. Current research has investigated some essential research areas concerning convection representation, the role of model horizontal resolution, cumulus parameterizations, and explicit convection on the diurnal precipitation characteristics of the Indian summer monsoon. Our investigation revealed that all current generation cumulus parameterizations (CPs), irrespective of their formulation, simulated noon, or afternoon peak precipitation phase-locked to the diurnal timing of maximum solar insolation over the Indian landmass; this is 3-6 h earlier than the observations. This misrepresentation may be due to the constant nature of the convective adjustment time scale. Also, we found marginal improvements in the diurnal precipitation amplitude and phase with the introduction of scale adaptive dynamic convective adjustment time scale in the MSKF, but several aspects of the diurnal precipitation characteristics were improperly simulated by the MSKF. As such, a better means to simulate the diurnal cycle in climate models is required. Further, we found realistic representation of Indian summer monsoon diurnal precipitation in a convection-permitting climate simulation. This simulation accurately reproduced the diurnal phase and amplitude of precipitation and its characteristics compared to the observations. This improvement in the diurnal cycle is due to the explicit representation of the convective adjustment time scales. In explicit convection simulations we found diurnal precipitation cycle spatial distribution dependance on the model horizontal resolution. These findings are useful to better understand typical diurnal precipitation characteristics biases among the climate models that utilized CPs and explicit convection.

The most fundamental mode of variability in the convection during Asian summer monsoon is a diurnal cycle of precipitation. Exact representation of such diurnal cycle of precipitation especially over land and ocean is a major problem in most of the sophisticated general circulation models (GCMs) and regional circulation models (RCMs). In this study, we simulate diurnal cycle of precipitation during south Asian summer monsoon using a suite of three ensemble experiments conducted at different spatial resolutions (25km, 12.5km, and 6.25km), with (convection on, CON) and without cumulus parameterization scheme (convection off, COFF). These continental scale simulations forced by Era-interim six hourly datasets for a period April 1 to October 31. The evaluation was performed on peak south Asian summer monsoon season (July-August) and, compared with Tropical Rainfall Measuring Mission (TRMM) three hourly datasets. The analysis shows no much impact of spatial resolution on the phase and amplitude of diurnal cycle precipitation over both land and ocean. Instead, explicit simulations showed marked changes and reproduced phase and amplitude of diurnal cycle precipitation as compared to the convection-parameterized simulations. Only in the explicit simulations, afternoon to late afternoon rainfall over land and early morning to afternoon rainfall over the Bay of Bengal was simulated well. In addition, the southward propagation of the diurnal peak precipitation in the Bay of Bengal was rightly captured in the explicit simulations, whereas in the convection-parameterized experiments, there was no such propagation and northward propagation was seen in the coarse spatial resolution simulations. This improvement in the explicit simulations over the ocean was due to the presence of a southward component of wind at the 600 hPa, which was not simulated in the convection-parameterized experiments. Over land region, in explicit simulations, due to higher solar insolation, increased the surface air temperature, which deepened the monsoon trough. As a result, moisture transport to the land from ocean amplified and availability of sufficiently higher convective available potential energy triggered convection in the late afternoon, which was not seen in convection parameterized simulations. These results define the prominence of the explicit convection or modified convection schemes in the models to better simulate the diurnal cycle precipitation of South Asian monsoon.

The global climate models (GCMs) and regional climate models (RCMs) represent large-scale features of the Indian summer monsoon (ISM) reasonably well. They unrealistically reproduce local to regional processes and contribute to the model simulation related spatial and temporal biases. It is believed that representation of topography with fine grid spacing could resolve the some of the biases in the ISM simulation in GCMs and RCMs. In fact, grid spacing reduces certain biases associated with the rainfall magnitude during ISM, but the phase of rainfall, intensity, and regional
scale-interactions remain untouched. In this study, by employing Weather Research and Forecasting model 3.8.1 as RCM, several first of its kind continental scale simulations are performed with different grid spacing’s (6.25km, 12.5km, and 25km) and convection on/off during ISM of 2012. The simulations utilise later and boundary conditions from the Era-interim reanalysis datasets, and runThe global climate models (GCMs) and regional climate models (RCMs) represent large-scale features of the Indian summer monsoon (ISM) reasonably well. They unrealistically reproduce local
to regional processes and contribute to the model simulation related spatial and temporal biases. It is believed that representation of topography with fine grid spacing could resolve the some of the biases in the ISM simulation in GCMs and RCMs. In fact, grid spacing reduces certain biases associated with the rainfall magnitude during ISM, but the phase of rainfall, intensity, and regional scale-interactions remain untouched. In this study, by employing Weather Research and Forecasting model 3.8.1 as RCM, several first of its kind continental scale simulations are performed with different grid spacing’s (6.25km, 12.5km, and 25km) and convection on/off during ISM of 2012. The
simulations utilise later and boundary conditions from the Era-interim reanalysis datasets, and run from April 1st to October 31st of 2012. The simulation results are verified qualitatively with India Meteorological Department rainfall gridded dataset and Tropical Rainfall Measurement Mission (TRMM). The analysis shows that convection-permitting simulation captures the fundamental aspects of the ISM preferably well. The regional scale features of monsoon rainfall characteristics are simulated realistically. During the peak monsoon season over core monsoon region, north-central, and southern peninsular India the diurnal rainfall peak is at late afternoon, afternoon, and early evening respectively. In case of convection-permitting simulations diurnal peak of rainfall is in very close agreement with the TRMM observations, whereas, finer grid spacing and convection parameterised simulations showed 3-6 hours earlier peak. Also, convection permitting simulation has reduced the significant biases over the Bay of Bengal as well. From the analysis, it is apparent that convection representation is more important than resolving topographic features. The exact representation of topography along with convection improves the models ability to simulate ISM.
from April 1st to October 31st of 2012. The simulation results are verified qualitatively with India Meteorological Department rainfall gridded dataset and Tropical Rainfall Measurement Mission (TRMM). The analysis shows that convection-permitting simulation captures the fundamental aspects of the ISM preferably well. The regional scale features of monsoon rainfall characteristics are simulated realistically. During the peak monsoon season over core monsoon region, north-central, and southern peninsular India the diurnal rainfall peak is at late afternoon, afternoon, and early
evening respectively. In case of convection-permitting simulations diurnal peak of rainfall is in very close agreement with the TRMM observations, whereas, finer grid spacing and convection parameterised simulations showed 3-6 hours earlier peak. Also, convection permitting simulation has reduced the significant biases over the Bay of Bengal as well. From the analysis, it is apparent that convection representation is more important than resolving topographic features. The exact representation of topography along with convection improves the models ability to simulate ISM.

This study investigated the reproducibility of rainfall characteristics of the Indian summer monsoon using a regional climate model (RCM), focusing on the convection representation and model horizontal grid resolution. To understand the importance of convection representation and model horizontal grid resolution, the study employed the Weather Research and Forecasting model WRFv3.8.1 as the RCM. Two series of experiments, that is, cumulus parameterization on/off (CON/COFF), were performed for the monsoon with three different spatial resolutions. Three contrasting monsoon years were selected for the simulations. The simulated rainfalls were evaluated with the India Meteorological Department data set and Tropical Rainfall Measurement Mission 3B42 Version 7. The results revealed that COFF captured fundamental aspects of the rainfall characteristics, such as diurnal cycle, rainfall intensity, and rainfall frequency. Over central India, in COFF, the diurnal precipitation peaks were simulated in afternoon/evening in close agreement with the observations. However, the diurnal precipitation peak in CON appeared 3-6 hr earlier than the observations. The diurnal precipitation variation was more associated with the horizontal grid resolution of the numerical model than representation of convection. Additionally, COFF could simulate diurnally propagating rainfall systems over the Bay of Bengal. Over the Indian land area, COFF simulated less-frequent intense precipitation systems, whereas CON simulated more-frequent widespread weak precipitation. This study demonstrated that convection representation is very important for simulation of diurnal rainfall systems over the Indian monsoon region, although refinement of model horizontal grid resolution is required over mountainous regions, where precipitation is closely related to orography.