TY  - JOUR
A1  - Cannon, Forest
A1  - Carvalho, Leila M. V.
A1  - Jones, Charles
A1  - Norris, Jesse
A1  - Bookhagen, Bodo
A1  - Kiladis, George N.
T1  - Effects of topographic smoothing on the simulation of winter precipitation in High Mountain Asia
JF  - Journal of Geophysical Research: Atmospheres
N2  - Numerous studies have projected future changes in High Mountain Asia water resources based on temperature and precipitation from global circulation models (GCMs) under future climate scenarios. Although the potential benefit of such studies is immense, coarse grid-scale GCMs are unable to resolve High Mountain Asia's complex topography and thus have a biased representation of regional weather and climate. This study investigates biases in the simulation of physical mechanisms that generate snowfall and contribute to snowpack in High Mountain Asia in coarse topography experiments using the Weather Research and Forecasting model. Regional snowpack is event driven, thus 33 extreme winter orographic precipitation events are simulated at fine atmospheric resolution with 6.67 km resolution topography and smoothed 1.85° × 1.25° GCM topography. As with many modified topography experiments performed in other regions, the distribution of precipitation is highly dependent on first-order orographic effects, which dominate regional meteorology. However, we demonstrate that topographic smoothing enhances circulation in simulated extratropical cyclones, with significant impacts on orographic precipitation. Despite precipitation reductions of 28% over the highest ranges, due to reduced ascent on windward slopes, total precipitation over the study domain increased by an average of 9% in smoothed topography experiments on account of intensified extratropical cyclone dynamics and cross-barrier moisture flux. These findings identify an important source of bias in coarse-resolution simulated precipitation in High Mountain Asia, with important implications for the application of GCMs toward projecting future hydroclimate in the region.
Y1  - 2017
U6  - https://doi.org/10.1002/2016JD026038
SN  - 2169-897X
SN  - 2169-8996
VL  - 122
IS  - 3
SP  - 1456
EP  - 1474
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Norris, Jesse
A1  - Carvalho, Leila M. V.
A1  - Jones, Charles
A1  - Cannon, Forest
A1  - Bookhagen, Bodo
A1  - Palazzi, Elisa
A1  - Tahir, Adnan Ahmad
T1  - The spatiotemporal variability of precipitation over the Himalaya: evaluation of one-year WRF model simulation
JF  - Climate dynamics : observational, theoretical and computational research on the climate system
N2  - The Weather Research and Forecasting (WRF) model is used to simulate the spatiotemporal distribution of precipitation over central Asia over the year April 2005 through March 2006. Experiments are performed at 6.7 km horizontal grid spacing, with an emphasis on winter and summer precipitation over the Himalaya. The model and the Tropical Rainfall Measuring Mission show a similar inter-seasonal cycle of precipitation, from extratropical cyclones to monsoon precipitation, with agreement also in the diurnal cycle of monsoon precipitation. In winter months, WRF compares better in timeseries of daily precipitation to stations below than above 3-km elevation, likely due to inferior measurement of snow than rain by the stations, highlighting the need for reliable snowfall measurements at high elevations in winter. In summer months, the nocturnal precipitation cycle in the foothills and valleys of the Himalaya is captured by this 6.7-km WRF simulation, while coarser simulations with convective parameterization show near zero nocturnal precipitation. In winter months, higher resolution is less important, serving only to slightly increase precipitation magnitudes due to steeper slopes. However, even in the 6.7-km simulation, afternoon precipitation is overestimated at high elevations, which can be reduced by even higher-resolution (2.2-km) simulations. These results indicate that WRF provides skillful simulations of precipitation relevant for studies of water resources over the complex terrain in the Himalaya.
KW  - WRF
KW  - Himalayas
KW  - Mesoscale
KW  - Precipitation
KW  - Climate change
KW  - Orographicprecipitation
KW  - Water resources
Y1  - 2017
U6  - https://doi.org/10.1007/s00382-016-3414-y
SN  - 0930-7575
SN  - 1432-0894
VL  - 49
SP  - 2179
EP  - 2204
PB  - Springer
CY  - New York
ER  -