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In this study, we performed a high‐resolution simulation using the Weather Research and Forecasting model, integrated with water vapor tracers, covering the years 2005–2019. Our objective was to obtain deeper insights into the spatiotemporal dynamics of external advected and local evaporative water vapor, and to elucidate their impact on precipitation patterns across the Tibetan Plateau (TP). Our findings underscore that a significant proportion of TP's precipitation originates from external advected water vapor, primarily entering through the western and southern boundaries. During summer, stronger zonal and meridional water vapor transport, driven by prevailing westerly winds and the Asian monsoon, significantly influences seasonal and spatial precipitation variations. Additionally, we observed that the inter‐annual variation of precipitation is intricately linked to changes in the net water vapor influx, modulated by alterations in atmospheric circulation. We also analyze the Precipitation Recycling Ratio (PRR) which refers to the proportion of precipitation originated from local evaporative water vapor to the total precipitation, revealing distinctive elevation‐dependent variations aligned with grassland distribution. Notably, PRR exhibits asynchronous shifts with precipitation at different timescales, potentially linked to soil moisture‐precipitation feedback at intra‐annual scales. Moreover, the investigation highlights that inter‐annual variations in PRR are primarily linked to the inflow and outflow of water vapor as well as wind strength at 500 hPa, particularly prominent during colder seasons, while thermal factors carry comparable weight to dynamical factors in warmer seasons. Plain Language Summary: Precipitation constitutes a vital component of the complex climatic conditions as well as the hydrological cycle over the Tibetan Plateau (TP), known as the "Asian Water Tower." Its distinct spatiotemporal variations, closely tied to the advected water vapor from external areas as well as evaporated within the TP, have direct impacts on local ecosystem and downstream water supply. These effects have profound socio‐economic and environmental consequences. In this study, we found that temporal variations and spatial inhomogeneities in precipitation are primarily impacted by the advection of external water vapor, mainly through atmospheric circulation. Additionally, about 18.9% of the annual precipitation stems from local evaporation, as indicated by the precipitation recycling ratio, which reflects the strength of regional land‐atmospheric interactions. Precipitation recycling processes are likely influenced by precipitation through soil moisture at intra‐annual timescale, but are notably impacted by the inflow of water vapor and wind strength at inter‐annual timescale. These results provide valuable insights into understanding precipitation variations at different spatiotemporal scales and contribute to more effective water resources management over the TP. Key Points: Precipitation recycling ratio (PRR) over the Tibetan Plateau exhibits significant variations both with elevation and from year to yearThe inter‐annual variation of precipitation is strongly influenced by the net influx of water vapor and associated atmospheric circulationsInter‐annual variation in PRR is significantly influenced by the inflow of water vapor and wind strength, especially during colder seasons [ABSTRACT FROM AUTHOR]

With the rapid global warming in recent decades, the Tibetan Plateau (TP) has suffered severe impacts, such as glacier retreat, glacial lake expansion, and permafrost degradation, which threaten the lives and properties of the local and downstream populations. Regional Reanalysis (RR) is vital for TP due to the limitations of observations. In this work, a 62-year (1961–2022) long atmospheric regional reanalysis with spatial resolution of 9 km (convective gray-zone scale) and temporal resolution of 1 hour over the TP (TPRR) was developed using the Weather Research and Forecasting (WRF) model, combined with re-initialization method, spectral nudging (SN), and several optimizations. TPRR is forced by ERA5 at hourly intervals. TPRR outperforms ERA5, realistically capturing climatological characteristics and seasonal variations of precipitation and T2m (air temperature at 2m above ground level). Moreover, TPRR better reproduces the frequency and intensity of precipitation, as well as the diurnal cycle of precipitation. This study also quantifies the wetting trend of 0.0071 mm/year over the TP amid global warming using TPRR. [ABSTRACT FROM AUTHOR]

Results from eight regional climate models (RCMs) participating in the Impact of Initialized Land Temperature and Snowpack on Sub-seasonal to Seasonal Prediction (LS4P) initiative of the Global Energy and Water Exchanges (GEWEX) are examined and compared with observations over the Tibetan Plateau (TP). The RCM common domain covers most areas of East Asia with a horizontal resolution of 20–30 km. The model simulation covers a period from April to September in each year between 1991 and 2015. This study explores the RCMs' ability for seasonal climate simulation over the TP, focusing on the summer monsoon climate as part of the LS4P initiative. An intercomparison is made among eight RCMs for precipitation, surface air temperature, mid-troposphere atmospheric circulation, moisture conditions, and surface energy fluxes. It shows that the downscaling characteristics differ significantly between two major RCM types. The RegCM4 models show positive precipitation biases over the entire TP, especially over the south and southeast TP, while the WRF models mostly show both positive and negative precipitation biases over the TP with relatively high spatial correlation between simulated and observed precipitation. The multi-model ensemble mean produces overall smaller precipitation biases than most individual RCMs, with the largest biases over the southeastern TP, and smaller surface air temperature biases over most areas of the TP, especially over the central and southwestern TP. Moreover, the ensemble mean can better reproduce the inter-annual variation of precipitation and surface air temperature than most RCMs with proper magnitude. Sensitivity analyses using RegCM4 with different physics parameterizations show that varying land and cumulus schemes may induce large precipitation differences over the TP by affecting moisture and atmospheric circulation conditions in the lower and upper troposphere, respectively. Moreover, turbulent heat and radiation fluxes differences are associated with the temperature differences between different RegCM4 models. [ABSTRACT FROM AUTHOR]

Climate models often overestimate the precipitation in western Tibetan Plateau (TP) during winter, due to their poor ability in representing the orographic drag of unresolved complex terrain. In this study, the parameterization scheme of orographic gravity wave drag (OGWD) in the Model for Prediction Across Scales (MPAS) is revised to account for the nonhydrostatic effects (NHE) on the surface momentum flux of vertically‐propagating orographic gravity waves (OGWs). The effect of revised OGWD scheme on the simulation of winter precipitation over the TP is examined using parallel numerical experiments with the original and revised schemes, respectively. The results show that the revised scheme can effectively alleviate the precipitation biases in western TP by improving the atmospheric circulation and water vapor transport (WVT). The NHE reduces the surface wave momentum flux of OGWs which results in weaker zonal OGWD in the mid‐low troposphere and thus stronger westerlies over the TP, reducing the easterly biases in the experiment with the original OGWD scheme. The weakened zonal OGWD promotes a plateau‐scale cyclonic circulation to the north of the TP, which suppresses the northern branch of the bifurcated westerlies detouring the TP. According to quantitative analysis, the WVT into the western TP and surrounding areas by upstream westerlies is notably reduced by the northeasterlies of the cyclonic circulation, which eventually leads to the decrease of precipitation in this region. Plain Language Summary: Precipitation over the TP greatly affects the regional hydrological cycle and has profound climate and socio‐economic implications. However, the winter precipitation in western TP is commonly overestimated in the state‐of‐the‐art climate models given their poor ability in representing the orographic drag effect of unresolved complex terrain. This study revises the parameterization scheme of OGWD in the Model for Prediction Across Scales (MPAS) by accounting for the nonhydrostatic effects on the upward‐propagating OGWs. The revised scheme is found to weaken the OGWD over the TP and enhance the westerlies. A plateau‐scale cyclonic circulation is induced to the north of the TP which suppresses the blocking and deflection of westerlies caused by the high terrain in western TP. Consequently, the water vapor transport by upstream westerlies is reduced, which effectively alleviate the precipitation biases in western TP. Key Points: Winter precipitation biases in western Tibetan Plateau (TP) are reduced using a nonhydrostatic orographic gravity wave drag (OGWD) schemeAccounting for the nonhydrostatic effects produces weaker zonal OGWD which induces a plateau‐scale cyclonic circulation to the north of TPThe cyclonic circulation counters the northern branch of bifurcated westerlies, leading to a reduced water vapor transport into western TP [ABSTRACT FROM AUTHOR]

The spatiotemporal characteristics of subdaily extreme precipitation over the Tibetan Plateau (TP) have undergone significant changes due to global warming. In this study, we employed the high‐resolution Weather Research and Forecasting regional climate model to conduct a series of historical and projection simulations under representative concentration pathways (RCPs), especially RCP4.5 and RCP8.5. The aim was to investigate the past and future climatologies and spatiotemporal evolution of subdaily precipitation extremes using newly proposed subdaily extreme precipitation indices (EPIs). The results show that projected changes in precipitation amount, particularly during wet hours, exhibit spatial disparaties. Notably, there are significant decreases along the southern border of the TP and over the western TP, while obvious increases are observed over the inner TP. The southeastern TP, western TP, and southern border of the TP are expected to experience less frequent, shorter duration, and more intense precipitation on an hourly basis. The TP, as a whole, has demonstrated significantly increasing trends in moderate‐to‐heavy precipitation frequencies, along with consistent decreasing trends in precipitation events with short, medium, and long durations. Furthermore, it is predicted that the relationship between extreme precipitation and temperature will deviate from the Clausius‐Clapeyron (C‐C) relationship toward the double C‐C relationship in the far‐future under RCP8.5, particularly over the southeastern TP. Additionally, there are robust correlations between the intensity‐related EPIs and elevation. This indicates that, at the local scale, the complex topography of the region may play a crucial role in shaping the nonuniform distribution of precipitation extremes by modulating associated upward motion. Plain Language Summary: The Tibetan Plateau (TP) has experienced substantial warming during the past decades, at a rate twice that of the global average due to its unique location and elevated terrain. Warming has significantly changed the amount, intensity, frequency, and extremes of precipitation over the TP. The changes in precipitation would influence the stability of the local ecoenvironment and the development of agriculture and industry directly. Previous studies have shown the big picture of daily precipitation extremes in the future, but the characteristics of precipitation extremes at hourly timescale are unclear. This study simulates the changes in subdaily precipitation extremes in the historical (1980–2005) and future (2006–2099) periods under different climate scenarios (RCP4.5 and RCP8.5). Our results show that the spatiotemporal changes and variability over the western TP, the southern border of TP and the southeastern TP are more dramatic than that over the central TP. The southeastern TP shows higher sensitivity and vulnerability to subdaily precipitation extremes and may experience less frequent precipitation lasting for a shorter duration, but with stronger intensity at hourly timescale. The results of this study can guide adaptive measures and be helpful for long‐term water resource management over the TP. Key Points: The simulated hourly precipitation over the Tibetan Plateau (TP) is characterized by heterogeneity and spatially disparate changesLess frequent, shorter duration, and more intense precipitation over the southeastern and the southern border of the TP are projectedThe distributions of the intensity‐related indices exhibit a dependency on elevation [ABSTRACT FROM AUTHOR]

The Tibetan Plateau (TP), also called the Third Pole, is considered to be "the world water tower". The northwestern TP (NWTP), which has an average elevation higher than 4800 m, is an arid region where the summer precipitation is largely overestimated by the ERA5 global reanalysis product. We hypothesize that this wet bias is mainly caused by unrealistic lower-level winds that trigger strong convection over the region; it can be reduced by using a high-resolution regional climate model with a large domain that allows realistically representing interactions between the Westerlies and Asian summer monsoons. Here, downscaling using the Weather Research and Forecasting (WRF) model driven by ERA5 was conducted with a large domain (8°‒50° N, 65°‒125° E) at 9 km for the period 1979‒2019 (WRF9km). Precipitation values from WRF9km and ERA5 were evaluated against satellite observations; compared with ERA5, WRF9km captured the climatological summer precipitation over the NWTP with a much-reduced wet bias. The ERA5 overestimation is mainly caused by excessive convective precipitation, likely linked to strong vertical motions over the NWTP induced by an overestimated lower-level southerly wind. [ABSTRACT FROM AUTHOR]

The Tibetan Plateau (TP) is an important component of the global climate system, while the characteristics of its climate are poorly represented in most regional climate models at coarse resolutions. In this study, a 20-year (2000–2019) dynamical downscaling simulation at the gray-zone resolution (9 km) using the WRF model driven by the ERA5 reanalysis is conducted over the TP. Based on comparisons against in-situ observations and the Integrated Multi-satellite Retrievals for GPM (IMERG) version 6 satellite precipitation product, the assessment of basic climate variables, such as near-surface air temperature (T2m) and precipitation, is performed to evaluate the model's performance and understand its added value better. Results show that both WRF and ERA5 can successfully reproduce the spatial patterns of annual mean and seasonal mean surface air temperature. However, significant cold and wet biases are found especially over the southeastern TP in ERA5, which are greatly improved in WRF with reduced RMSEs. Not only the climatological characteristics, but also the inter-annual variability and seasonal variation of T2m and precipitation are well captured by WRF which reduces the cold and wet biases especially in winter and summer compared to ERA5, respectively. Besides, at daily scale, the overestimation of precipitation in WRF and ERA5 is mainly caused by the overestimated precipitation frequency when precipitation intensity changed slightly. Furthermore, WRF outperforms ERA5 in capturing the diurnal variation of precipitation with more realistic peak time in all sub-regions over the TP. Further investigation into the mechanism of model bias reveals that less simulated snow cover fraction plays a crucial role in increasing the surface net energy by affecting surface albedo over the southeastern TP in WRF, leading to higher T2m. In addition, less water vapor transport from the southern boundary of TP leads to reduced wet bias in WRF, indicating that the added value in dynamical downscaling at gray-zone resolution is obtained by representing water vapor transport more realistically. [ABSTRACT FROM AUTHOR]

The Tibetan Plateau (TP) is often referred to as 'the Third Pole' and plays an essential role in the global climate. However, it remains challenging for most global and regional models to realistically simulate the characteristics of climate over the TP. In this study, two Weather Research and Forecasting model (WRF) experiments using spectral nudging with gray-zone (GZ9) and convection-permitting (CP3) resolution are conducted for summers from 2009 to 2018. The surface air temperature (T2m) and precipitation from the two simulations and the global reanalysis ERA5 are evaluated against in-situ observations. The results show that ERA5 has a general cold bias over southern TP, especially in maximum T2m (Tmax), and wet bias over whole TP. Both experiments can successfully capture the spatial pattern and daily variation of T2m and precipitation, though cold bias for temperature and dry bias for precipitation exist especially over the regions south of 35° N. Compared with ERA5, the added value of the two WRF experiments is mainly reflected in the reduced cold bias especially for Tmax with more improvement found in CP3 and the reduced wet bias. However, the ability of the convection-permitting WRF experiment in improving the simulation of precipitation seems limited when compared to the gray-zone WRF experiment, which may be related to the biases in physical parameterization and lack of representativeness of station observation. Further investigation into surface radiation budget reveals that the underestimation of net shortwave radiation contributes a lot to the cold bias of T2m over the southeastern TP in GZ9 which is improved in CP3. Compared with GZ9, CP3 shows that larger specific humidity at low-level (mid-high level) coexists with more precipitation (clouds) over the southern TP. This improvement is achieved by better depiction of topographic details, underlying surface and atmospheric processes, land–atmosphere interactions and so on, leading to stronger northward water vapor transport (WVT) in CP3, providing more water vapor for precipitation at surface and much wetter condition in the mid-high level. [ABSTRACT FROM AUTHOR]

Driven by the outputs of four global climate models from Coupled Model Intercomparison Project Phase 5, a long-term downscaling and projection under the RCP8.5 scenario is conducted within the Coordinated Regional Downscaling Experiment East Asia phase II framework with Weather Research and Forecasting Model (WRF) and Regional Climate Model version 4 (RegCM4). All the single simulations and the ensembles well reproduce the spatial pattern of the precipitation amount over East Asia with the spatial correlations (SCORs) larger than 0.58, although bias exists in some areas. The models also reasonably present the spatial patterns of the extreme precipitation indices except the Rx5day (annual maximum consecutive 5-day precipitation) and the consecutive dry days (CDD), with the SCORs ranging between 0.43 and 0.71. In general, WRF outperforms RegCM4 in producing the spatial patterns of most extreme precipitation indices and RegCM4 generates lower root mean square errors. In the future, the precipitation amount would significantly increase in northeastern China and northwestern China and over the Tibetan Plateau, which is mainly due to the increase of precipitation intensity in WRF and frequency in RegCM4. The extreme frequency and intensity indices are projected to significantly increase over the Tibetan Plateau and some areas of northwestern China. In addition, the consecutive wet days will get significantly longer in the above regions, where the consecutive dry days will shorten, indicating more consecutive precipitation events in the future. The change in the probability distribution of the extreme indices reveals that stronger and longer-duration extreme precipitation events would get more frequent in the future. The increase of low-level specific humidity can partly explain the increase of precipitation. [ABSTRACT FROM AUTHOR]

To explore the driving mechanisms of elevation-dependent warming (EDW) over the Tibetan Plateau (TP), the output from a suite of numerical experiments with different cumulus parameterization schemes (CPs) under the Coordinated Regional Climate Downscaling Experiments-East Asia (CORDEX-EA-II) project is examined. Results show that all experiments can broadly capture the observed temperature distributions over the TP with consistent cold biases, and the spread in temperature simulations commonly increases with elevation with the maximum located around 4000–5000 m. Such disagreements among the temperature simulations could to a large extent be explained by their spreads in the surface albedo feedback (SAF). All the experiments reproduce the observed EDW below 5000 m in winter but fail to capture the observed EDW above 4500 m in spring. Further analysis suggests that the simulated EDW during winter is mainly caused by the SAF, and the clear-sky downward longwave radiation (LWclr) plays a secondary role in shaping EDW. The models' inability in simulating EDW during spring is closely related to the SAF and the surface cloud radiative forcing (CRFs). Furthermore, the magnitude and structure of the simulated EDW are sensitive to the choice of CPs. Different CPs generate diverse snow cover fractions, which can modulate the simulated SAF and its effect on EDW. Also, the CPs show great influence on the LWclr via altering the low-level air temperature. Additionally, the mechanism for different temperature changes among the experiments varies with altitudes during summer and autumn, as the diverse temperature changes appear to be caused by the LWclr for the low altitudes while by the SAF for the middle-high altitudes. [ABSTRACT FROM AUTHOR]

Under the Coordinated Regional Climate Downscaling Experiments‐East Asia (CORDEX‐EA‐II), the outputs from two regional climate models (RCMs) driven by four global climate models (GCMs) are used to investigate the characteristics and possible mechanisms of the projected elevation‐dependent warming (EDW) over the Tibetan Plateau (TP) under the Representative Concentration Pathway emission scenario 8.5 (RCP8.5). Results show that widespread warming over the TP is projected with considerable disagreements in warming intensity and the maximum warming center among RCMs. The largest spread in the surface air temperature (Tas) projections is found above 5,000 m, indicating that a large uncertainty exists over the higher elevations. A marked EDW signal over the TP is simulated under the RCP 8.5 by the multi‐RCM ensemble mean for all seasons, particularly in autumn. Based on the analysis of the surface energy budget, it is found that the surface albedo feedback (SAF) is the primary contributor to EDW and acts as the main source of uncertainty in EDW projections among RCMs. The downward longwave radiation (DLW) is found to be the dominant factor in regulating Tas change over the TP, and its contribution to EDW is model‐dependent. Furthermore, the structure and magnitude of projected EDW are sensitive to the RCM physics and driving GCM, as they can alter the projections of snow cover and albedo, which modulate the simulated SAF and its effect on EDW. Additionally, RegCM4 shows a higher sensitivity to the anthropogenic greenhouse forcing than WRF, evidenced by the larger temperature projections and stronger EDW signal in RegCM4. Key Points: Elevation‐dependent warming will happen in the future with its magnitude and structure varying with seasonsSurface albedo feedback is the primary contributor to elevation‐dependent warming and the dominant source of uncertainty in its projectionsThe projected elevation‐dependent warming depends not only on the driving global climate model but also on the internal model physics [ABSTRACT FROM AUTHOR]

The Tibetan Plateau (TP) has undergone significant climate warming with a stronger amplitude than that experienced elsewhere in the Northern Hemisphere during the past years, but it is still challenging for most regional climate models to realistically simulate the present-day climate and promisingly project the future climate over the TP. In this study, high-resolution simulation using the Weather Research and Forecasting model (WRF) driven by bias-corrected CESM is conducted from 1979 to 2100, with the period from 2006 to 2100 under RCP4.5 and RCP8.5 (Representative Concentration Pathways) scenarios. The simulated present-day climate is evaluated firstly and then the future climate is studied secondly. The results show that compared with station observation, WRF successfully captures the spatial pattern of annual mean surface air temperature (T2m) and precipitation over the TP, with the spatial correlation coefficients larger than 0.95 for T2m and larger than 0.70 for precipitation. However, great underestimation of T2m over the southeastern TP is found in the cold season which is related to the underestimation of snow there, and the snow-temperature positive feedback develops. WRF shows limited ability in reducing the dry bias in summer, which is related to the simulated weaker water vapor transport over the southern and eastern TP. For the future changes, substantial warming, general increase in precipitation and decrease in snow are projected under RCP8.5. The warming magnitude is greater over the western TP where the more significant decrease of snow will occur by the end of 21st century. Projected precipitation tends to consistently decrease over the western TP and along the south flank of TP which is related to the low-level circulation change. The occurring frequency of light precipitation will decrease while that of non-precipitation and extreme precipitation will increase especially in the far future, with the more obvious change occurring under RCP8.5. Overall, WRF shows high ability in simulating the present-day climate and thus reliable performance in future climate projection. • High-resolution WRF historical simulation can successfully reproduce the annual and seasonal mean climate over the TP. • The cold bias is related to the overestimated snow, and the dry bias is related to the weaker water vapor transport. • Substantial warming and decrease in snow are projected over the western TP by the end of 21st century under RCP8.5. [ABSTRACT FROM AUTHOR]

The Tibetan Plateau (TP) holds a pivotal position in regional and global climate, whereas the atmospheric characteristics vary greatly in the simulation with different physical parameterization schemes at the gray-zone scale (around 9 km). In this study, 24 sets of experiments were set up with different cumulus parameterization schemes (CPSs), microphysics parameterization schemes (MPSs) and planetary boundary layer parameterization schemes (PBLSs) using the WRF model driven by the ERA5 reanalysis to explore the sensitivity and try to summarize a combination of parameterization schemes suitable for the simulation over TP. Based on comparisons against in-situ observations, most CPS experiments showed large wet bias and overestimated occurrence of precipitation events, and CTL without CPS and CU6 with Tiedtke CPS show better performance at gray-zone scale. The influence of MPS and PBLS is less than CPS on the simulation, and Thompson MPS and UW PBLS showed a better performance. Most of the CPS experiments reach an earlier and more intensive peak compared to the Integrated Multi-satellite Retrievals for GPM (IMERG) version 6 satellite precipitation product, except CTL, CU11, and CU6, which show closer but weaker peaks. CPS experiments simulate more precipitation associated with water vapor transporting into TP and anomalous cyclonic circulation against CTL. The less water vapor transport from the south edge of TP in the CTL against CU14, CU16, and CU2, leads to more local precipitation. Graupel particles and the warm-rain process play a crucial role in the precipitation simulation with different MPSs. Although with less water vapor in the low atmosphere, MP2 simulates more precipitation due to more graupel particles and warm-rain processes against CTL. PBLSs have a substantial impact on latent heat, then influence evaporation and precipitation. The lower PBL height usually leads to more latent heat and more precipitation. • Thompson, UW and Tiedtke schemes perform better based on sensitivity analysis • CPSs affect precipitation mainly through low-level circulation and related WVT • MPSs modulate the VIWV and hydrometer particles to affect precipitation • PBLSs exert indirect influence on precipitation through surface latent heat flux [ABSTRACT FROM AUTHOR]