Department of Geography

Reliable subseasonal-to-seasonal (S2S) precipitation prediction is highly desired due to the great socioeconomical implications, yet it remains one of the most challenging topics in the weather/climate prediction research area. As part of the Impact of Initialized Land Temperature and Snowpack on Sub-seasonal to Seasonal Prediction (LS4P) project of the Global Energy and Water Exchanges (GEWEX) program, twenty-one climate models follow the LS4P protocol to quantify the impact of the Tibetan Plateau (TP) land surface temperature/subsurface temperature (LST/SUBT) springtime anomalies on the global summertime precipitation. We find that nudging towards reanalysis winds is crucial for climate models to generate atmosphere and land surface initial conditions close to observations, which is necessary for meaningful S2S applications. Simulations with nudged initial conditions can better capture the summer precipitation responses to the imposed TP LST/SUBT spring anomalies at hotspot regions all over the world. Further analyses show that the enhanced S2S prediction skill is largely attributable to the substantially improved initialization of the Tibetan Plateau-Rocky Mountain Circumglobal (TRC) wave train pattern in the atmosphere. This study highlights the important role that initial condition plays in the S2S prediction and suggests that data assimilation technique (e.g., nudging) should be adopted to initialize climate models to improve their S2S prediction.

Abstract: Subseasonal to seasonal (S2S) prediction of droughts and floods is one of the major challenges of weather and climate prediction. Recent studies suggest that the springtime land surface temperature/subsurface temperature (LST/SUBT) over the Tibetan Plateau (TP) can be a new source of S2S predictability. The project “Impact of Initialized Land Surface Temperature and Snowpack on Subseasonal to Seasonal Prediction (LS4P)” was initiated to study the impact of springtime LST/SUBT anomalies over high mountain areas on summertime precipitation predictions. The present work explores the simulated global scale response of the atmospheric circulation to the springtime TP land surface cooling by 16 current state-of-the-art Earth System Models (ESMs) participating in the LS4P Phase I (LS4P-I) experiment. The LS4P-I results show, for the first time, that springtime TP surface anomalies can modulate a persistent quasi-barotropic Tibetan Plateau-Rocky Mountain Circumglobal (TRC) wave train from the TP via the northeast Asia and Bering Strait to the western part of the North America, along with the springtime westerly jet from TP across the whole North Pacific basin. The TRC wave train modulated by the TP thermal anomaly play a critical role on the early summer surface air temperature and precipitation anomalies in the regions along the wave train, especially over the northwest North America and the southern Great Plains. The participant models that fail in capturing the TRC wave train greatly under-predict climate anomalies in reference to observations and the successful models. These results suggest that the TP LST/SUBT anomaly via the TRC wave train is the first order source of the S2S variability in the regions mentioned. Furthermore, the TP surface temperature anomaly can influence the Southern Hemispheric circulation by generating cross-equator wave trains. However, the simulated propagation pathways from the TP into the Southern Hemisphere show large inter-model differences. More dynamical understanding of the TRC wave train as well as its cross-equator propagation into the Southern Hemisphere will be explored in the newly launched LS4P phase II experiment.

This study is an analysis of records of the seizure of otters by law enforcement agencies in selected Asian countries between 1980 and July 2015. The study was undertaken to understand the extent and scale of the illegal otter trade in Asia, and focussed on four Asian otter species i.e., the eurasian otter (Lutra lutra), hairy-nosed otter (Lutra sumatrana), small-clawed otter (Aonyx cinereus), and the smooth-coated otter (Lutrogale perspicillata). All four species were documented in illegal trade, with 161 recorded otter seizures across 15 countries in Asia between 1980 and 2015, involving an estimated 5881 individuals. Otter skins constituted the majority of the seizures, particularly in India, Nepal and China. Since early 2000s, there seems to be a rising demand for otter pups for the pet trade, particularly in Indonesia, Malaysia, Thailand and Viet Nam. While seizure records as a whole were scarce across the region, we conclude that illegal otter trade is persistent and largely unchecked, despite otter species being legally protected across their range.

A survey for otters across Mongolia was conducted in 2012 to document the status and distribution range of the Eurasian otter (Lutra lutra Linnaeus, 1758), and to propose the scientific basis for government policies to protect the species. We report results from the first survey of otter since the late 1980s (Stubbe et al., 1989), with new records emerged after 2012. The species is very rarely reported in the country, but in addition to an actual sighting of this species, the survey team observed a limited number of otter sign, including tracks, scat, ice diving holes, snow diving marks, snow wallows, territorial marks, and prey remains at widely distributed sites. We recommend a set of strategies to expand conservation for the Eurasian otter in Mongolia.

We report the findings of the first survey for Eurasian otter (Lutra lutra) from the Upper Indus River and several of its tributaries in Leh and Kargil Districts, India. The survey was conducted between 25th August to 30th October, 2015. We report the distribution of otter sign, including camera trap images, scats, tracks, and latrines, and the habitat characteristics along 50 km of riverbank. We observed indirect sign of otter presence on two of the four rivers surveyed, but otter abundance appears to be low in the area. Human disturbance, including proximity to settlements, grazing livestock, and particularly feral dogs, appears to deter otter presence.

Abstract: We report the findings of a survey for otters along a major river in central Bhutan. The river bears various names in different stretches along its run, including Mochhu, Phochhu, Punatsangchhu and Sunkosh. We report: 1) the distribution and density of otter sign, including tracks, scats, latrines and dens, 2) the correlation between sign abundance and vegetation and substrate characteristics, and 3) the correlation of otter sign with human disturbance. Five of the six 5.5 km transects sampled were positive for otter sign. The one transect with no otter sign was the site of a recent severe flood event. Linear sign density was 9.4 sign km-1 along one bank of the river, with a mean of 45% of two sample rounds positive for presence of otter sign in sample plots. The Kamichhu site possessed the highest percentage of positive plots at 95%, and the Sunkosh site the lowest at 35%. The number of otter sign was positively correlated with bankside vegetation and with sandy beaches with large boulders. Human disturbance also influenced the density of otter sign, with proximity of settlements, represented by the presence of footpaths, grazing and trash, apparently deterring otter presence. Three species of otters likely occupy the rivers of Bhutan (Lutrogale perspillata, Lutra lutra, and Aonyx cinereus) but since altitudinal niche partitioning by these species is not understood in the study area, we make no attempt to predict distribution by species. Only one otter species, a smooth-coated otter (L. perspicillata) was directly sighted.