Implementation of a turbulent orographic form drag scheme in WRF and its application to the Tibetan Plateau

Zhou, Xu; Yang, Kun; Wang, Yan

doi:10.1007/s00382-017-3677-y

Cited by 57 publications

(40 citation statements)

References 36 publications

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“…In the high mountains of the WTP, interactions between complex topography and atmospheric circulations affect how precipitation varies with altitude (Bookhagen and Burbank, 2006;Immerzeel et al, 2014;Lin et al, 2018;Zhou et al, 2018). Observation stations in the mountainous areas of the WTP are sparse and mostly distributed in valley bottoms, which receive relatively little precipitation.…”

Section: Altitudinal-dependence Of Precipitationmentioning

confidence: 99%

Characterizing precipitation in high altitudes of the western Tibetan plateau with a focus on major glacier areas

Yang

Tang

et al. 2020

Intl Journal of Climatology

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Solid water resources such as glaciers and snow cover are widely distributed in the western Tibetan plateau (WTP), and precipitation is the key supply of them. However, the characteristics of precipitation over the WTP remain unclear due to sparse observations. Using observation-based gridded data (APHRODITE, GPCC), satellite products (TRMM, GPM), reanalysis data (ERA5, ERA-Interim, JRA-55) and weather research and forecasting model (WRF)-simulation data (HAR10, HAR30), this study investigated the precipitation characteristics in high mountain areas (altitude >2,500 m a.s.l.) of the WTP (26-44 N, 70-85 E) from 2001 to 2013. Results show that annual GPM precipitation (336 mm) is much lower than that of other data sets (570-800 mm) for the WTP and appears to be an outlier; meanwhile, the other data sets show increasing precipitation as grid resolution decreases (becomes coarser). In contrast, high spatial resolution WRF simulations (HAR10, HAR30) yielded considerably higher precipitation in four strongly glacierized alpine areas (Western Himalaya, Karakorum, Tajikistan, and west Kunlun) than the other data sets. When compared to precipitation estimated using the water balance in nine glacierized catchments of the Upper Indus River Basin, the HAR data sets more reasonably represent the amount of precipitation in high mountain areas than the other data sets. The surface albedo, snow cover extent, and snow cover duration observed by satellites further indicate that the HAR data sets yield reasonable spatial variability of precipitation. This implies that the commonly used data sets (such as observation data and satellite products) underestimate the precipitation in high mountain areas. According to the HAR10 data, the four major glacierized areas on the WTP have similar precipitation amounts in summer and autumn, and the winter-spring contribution to annual precipitation is at least 70% in three of these areas (Western Himalaya, Karakorum, and Tajikistan). This pattern indicates that precipitation over the high-altitude areas in WTP is mainly controlled by the mid-latitude westerlies. The annual precipitation in these areas is over 1,000 mm, which is comparable to that of the southeast TP but much larger than that on the central plateau. Therefore, the spatial precipitation pattern across the TP is 'wet east and west, dry middle'.

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Section: Altitudinal-dependence Of Precipitationmentioning

confidence: 99%

Characterizing precipitation in high altitudes of the western Tibetan plateau with a focus on major glacier areas

Yang

Tang

et al. 2020

Intl Journal of Climatology

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“…WRF2 further weakens simulated wind speed and WVT from WRF10 to a lesser extent, which may have to do with the fact that TOFD is explicitly resolved in WRF2. Indeed, by inducing the TOFD scheme developed by Beljaars et al (2004) to WRF with a resolution of 0.25°, Zhou et al (2017) were able to improve the simulation of both near-surface and upper-air wind fields over the TP. The variance of subgridscale orography is extremely high (up to 50 000 m 2 ) over the slopes of the Himalayas for a 10 km grid spacing (figure not shown); this points to the necessity of considering subgrid drag with such a resolution.…”

Section: Behind the Resolution Dependency Of Simulated Wvtmentioning

confidence: 99%

Impact of model resolution on simulating the water vapor transport through the central Himalayas: implication for models’ wet bias over the Tibetan Plateau

et al. 2018

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Current climate models commonly overestimate precipitation over the Tibetan Plateau (TP), which limits our understanding of past and future water balance in the region. Identifying sources of such models' wet bias is therefore crucial. The Himalayas is considered a major pathway of water vapor transport (WVT) towards the TP. Their steep terrain, together with associated small-scale processes, cannot be resolved by coarse-resolution models, which may result in excessive WVT towards the TP. This paper, therefore, investigated the resolution dependency of simulated WVT through the central Himalayas and its further impact on precipitation bias over the TP. According to a summer monsoon season of simulations conducted using the weather research forecasting (WRF) model with resolutions of 30, 10, and 2 km, the study found that finer resolutions (especially 2 km) diminish the positive precipitation bias over the TP. The higher-resolution simulations produce more precipitation over the southern Himalayan slopes and weaker WVT towards the TP, explaining the reduced wet bias. The decreased WVT is reflected mostly in the weakened wind speed, which is due to the fact that the high resolution can improve resolving orographic drag over a complex terrain and other processes associated with heterogeneous surface forcing. A significant difference was particularly found when the model resolution is changed from 30 to 10 km, suggesting that a resolution of approximately 10 km represents a good compromise between a more spatially detailed simulation of WVT and computational cost for a domain covering the whole TP.

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“…The GF drag also shows effective contributions, though it may cause too Journal of Geophysical Research: Atmospheres 10.1002/2017JD027212 strong drag at the surface. With the above evaluations and discussions, we suggest that TOFD scheme from Beljaars et al (2004) implemented by Zhou et al (2017) should be switched on in the WRF model to simulate a more realistic atmospheric circulation (especially for regional simulations over the TP in winter). The GWD/FB scheme implemented by Choi and Hong (2015) might be optional, and one may expect more benefits for large-scale simulations, for example, a global run.…”

Section: 1002/2017jd027212mentioning

confidence: 99%

“…An insufficient representation of subgrid orography can lead to systematic biases in numerical weather prediction and climate models (Palmer et al, 1986;Wu & Chen, 1985), especially for the complex Tibetan Plateau (TP), where the direct orographic impacts are stronger than over flat regions. Thus, Zhou et al (2017) incorporated a new TOFD scheme in WRF, which follows an exponential decay of drag with altitude, developed by Beljaars et al (2004) (hereafter BBW scheme). It is worth mentioning that the JD12 scheme is stability dependent (Lorente-Plazas et al, 2016) while the BBW scheme is not.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of WRF Simulations With Different Selections of Subgrid Orographic Drag Over the Tibetan Plateau

et al. 2017

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Weather Research and Forecasting (WRF) simulations with different selections of subgrid orographic drag over the Tibetan Plateau have been evaluated with observation and ERA‐Interim reanalysis. Results show that the subgrid orographic drag schemes, especially the turbulent orographic form drag (TOFD) scheme, efficiently reduce the 10 m wind speed bias and RMS error with respect to station measurements. With the combination of gravity wave, flow blocking and TOFD schemes, wind speed is simulated more realistically than with the individual schemes only. Improvements are also seen in the 2 m air temperature and surface pressure. The gravity wave drag, flow blocking drag, and TOFD schemes combined have the smallest station mean bias (−2.05°C in 2 m air temperature and 1.27 hPa in surface pressure) and RMS error (3.59°C in 2 m air temperature and 2.37 hPa in surface pressure). Meanwhile, the TOFD scheme contributes more to the improvements than the gravity wave drag and flow blocking schemes. The improvements are more pronounced at low levels of the atmosphere than at high levels due to the stronger drag enhancement on the low‐level flow. The reduced near‐surface cold bias and high‐pressure bias over the Tibetan Plateau are the result of changes in the low‐level wind components associated with the geostrophic balance. The enhanced drag directly leads to weakened westerlies but also enhances the a‐geostrophic flow in this case reducing (enhancing) the northerlies (southerlies), which bring more warm air across the Himalaya Mountain ranges from South Asia (bring less cold air from the north) to the interior Tibetan Plateau.

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Implementation of a turbulent orographic form drag scheme in WRF and its application to the Tibetan Plateau

Cited by 57 publications

References 36 publications

Characterizing precipitation in high altitudes of the western Tibetan plateau with a focus on major glacier areas

Characterizing precipitation in high altitudes of the western Tibetan plateau with a focus on major glacier areas

Impact of model resolution on simulating the water vapor transport through the central Himalayas: implication for models’ wet bias over the Tibetan Plateau

Evaluation of WRF Simulations With Different Selections of Subgrid Orographic Drag Over the Tibetan Plateau

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