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 - TY - JOUR A1 - Smith, Taylor A1 - Bookhagen, Bodo A1 - Cannon, Forest T1 - Improving semi-automated glacier mapping with a multi-method approach: applications in central Asia JF - The Cryosphere : TC ; an interactive open access journal of the European Geosciences Union N2 - Studies of glaciers generally require precise glacier outlines. Where these are not available, extensive manual digitization in a geographic information system (GIS) must be performed, as current algorithms struggle to delineate glacier areas with debris cover or other irregular spectral profiles. Although several approaches have improved upon spectral band ratio delineation of glacier areas, none have entered wide use due to complexity or computational intensity. In this study, we present and apply a glacier mapping algorithm in Central Asia which delineates both clean glacier ice and debris-covered glacier tongues. The algorithm is built around the unique velocity and topographic characteristics of glaciers and further leverages spectral and spatial relationship data. We found that the algorithm misclassifies between 2 and 10% of glacier areas, as compared to a similar to 750 glacier control data set, and can reliably classify a given Landsat scene in 3-5 min. The algorithm does not completely solve the difficulties inherent in classifying glacier areas from remotely sensed imagery but does represent a significant improvement over purely spectral-based classification schemes, such as the band ratio of Landsat 7 bands three and five or the normalized difference snow index. The main caveats of the algorithm are (1) classification errors at an individual glacier level, (2) reliance on manual intervention to separate connected glacier areas, and (3) dependence on fidelity of the input Landsat data. Y1 - 2015 U6 - https://doi.org/10.5194/tc-9-1747-2015 SN - 1994-0416 SN - 1994-0424 VL - 9 IS - 5 SP - 1747 EP - 1759 PB - Copernicus CY - Göttingen ER - TY - GEN A1 - Smith, Taylor A1 - Bookhagen, Bodo A1 - Cannon, Forest T1 - Improving semi-automated glacier mapping with a multi-method approach BT - applications in central Asia T2 - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe N2 - Studies of glaciers generally require precise glacier outlines. Where these are not available, extensive manual digitization in a geographic information system (GIS) must be performed, as current algorithms struggle to delineate glacier areas with debris cover or other irregular spectral profiles. Although several approaches have improved upon spectral band ratio delineation of glacier areas, none have entered wide use due to complexity or computational intensity. In this study, we present and apply a glacier mapping algorithm in Central Asia which delineates both clean glacier ice and debris-covered glacier tongues. The algorithm is built around the unique velocity and topographic characteristics of glaciers and further leverages spectral and spatial relationship data. We found that the algorithm misclassifies between 2 and 10% of glacier areas, as compared to a similar to 750 glacier control data set, and can reliably classify a given Landsat scene in 3-5 min. The algorithm does not completely solve the difficulties inherent in classifying glacier areas from remotely sensed imagery but does represent a significant improvement over purely spectral-based classification schemes, such as the band ratio of Landsat 7 bands three and five or the normalized difference snow index. The main caveats of the algorithm are (1) classification errors at an individual glacier level, (2) reliance on manual intervention to separate connected glacier areas, and (3) dependence on fidelity of the input Landsat data. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 510 KW - debris-covered glaciers KW - land ice measurements KW - remote-sensing data KW - thematic mapper KW - glims project KW - aster data KW - inventory KW - area KW - deformation KW - parameters Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-408471 SN - 1866-8372 IS - 510 ER - 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 -