Monitoring the Monsoon in the Himalayas: Observations in Central Nepal, June 2001

Barros, A. P.; Lang, Timothy J.

doi:10.1175/1520-0493(2003)131<1408:mtmith>2.0.co;2

Cited by 182 publications

(184 citation statements)

References 30 publications

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“…Similar results were obtained from station-based observations in different regions of Nepal where precipitation peaks around 2500-3600 mm and decreases further with increase in altitude in high mountain regions [48][49][50][51]. In addition to the horizontal and altitudinal precipitation gradients, a large seasonal precipitation gradient (~factor of 4) has also been observed over a short horizontal distance of ~10 km in MRB [52].…”

Section: Study Areasupporting

confidence: 83%

“…In the DHM database, the longest precipitation record available since 1946 is from only three stations, although there are records from 23 stations since 1947, and from around 40 stations since 1950. Until 1956, the precipitation observations were available only from the stations located In addition to the horizontal and altitudinal precipitation gradients, a large seasonal precipitation gradient (~factor of 4) has also been observed over a short horizontal distance of~10 km in MRB [52].…”

Section: Datamentioning

confidence: 99%

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Rising Precipitation Extremes across Nepal

Karki

Hasson

Schickhoff

et al. 2017

Climate

206

140

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Abstract:As a mountainous country, Nepal is most susceptible to precipitation extremes and related hazards, including severe floods, landslides and droughts that cause huge losses of life and property, impact the Himalayan environment, and hinder the socioeconomic development of the country. Given that the countrywide assessment of such extremes is still lacking, we present a comprehensive picture of prevailing precipitation extremes observed across Nepal. First, we present the spatial distribution of daily extreme precipitation indices as defined by the Expert Team on Climate Change Detection, Monitoring and Indices (ETCCDMI) from 210 stations over the period of . Then, we analyze the temporal changes in the computed extremes from 76 stations, featuring long-term continuous records for the period of 1970-2012, by applying a non-parametric Mann−Kendall test to identify the existence of a trend and Sen's slope method to calculate the true magnitude of this trend. Further, the local trends in precipitation extremes have been tested for their field significance over the distinct physio-geographical regions of Nepal, such as the lowlands, middle mountains and hills and high mountains in the west (WL, WM and WH, respectively), and likewise, in central (CL, CM and CH) and eastern (EL, EM and EH) Nepal. Our results suggest that the spatial patterns of high-intensity precipitation extremes are quite different to that of annual or monsoonal precipitation. Lowlands (Terai and Siwaliks) that feature relatively low precipitation and less wet days (rainy days) are exposed to high-intensity precipitation extremes. Our trend analysis suggests that the pre-monsoonal precipitation is significantly increasing over the lowlands and CH, while monsoonal precipitation is increasing in WM and CH and decreasing in CM, CL and EL. On the other hand, post-monsoonal precipitation is significantly decreasing across all of Nepal while winter precipitation is decreasing only over the WM region. Both high-intensity precipitation extremes and annual precipitation trends feature east−west contrast, suggesting significant increase over the WM and CH region but decrease over the EM and CM regions. Further, a significant positive trend in the number of consecutive dry days but significant negative trend in the number of wet (rainy) days are observed over the whole of Nepal, implying the prolongation of the dry spell across the country. Overall, the intensification of different precipitation indices over distinct parts of the country indicates region-specific risks of floods, landslides and droughts. The presented findings, in combination with population and environmental pressures, can support in devising the adequate region-specific adaptation strategies for different sectors and in improving the livelihood of the rural communities in Nepal.

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Section: Study Areasupporting

confidence: 83%

Section: Datamentioning

confidence: 99%

Rising Precipitation Extremes across Nepal

Karki

Hasson

Schickhoff

et al. 2017

Climate

206

140

View full text Add to dashboard Cite

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“…To show that the cyclonic flow over the Ganges Basin and IG LLJ does not reflect the mean of many transient events and a mean flow persists, we decompose the total moisture flux over the region for the JRA55 during July and August (S3) and show the temporal monthly distribution of zonal winds over the IGP transect (blue line in Figure 1a) from May to September (S4). We briefly evaluate the possibility that the easterly flow is induced by changes in diurnal heating over topographic slopes [Barros and Lang, 2003] and show four-times daily output of the zonally averaged winds for JRA55 (S5).…”

Section: Observationsmentioning

confidence: 99%

The neglected Indo‐Gangetic Plains low‐level jet and its importance for moisture transport and precipitation during the peak summer monsoon

Acosta

Huber

2017

Geophysical Research Letters

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Accurately simulating the Indo‐Asian monsoon (IAM) using atmospheric general circulation models (AGCMs) is challenging but crucial. This study uses reanalysis products European Centre of Medium‐Range Forecast Interim reanalysis, Japanese Reanalysis year 55, and High Asia Reanalysis to highlight an easterly, low‐level barrier jet along the Indo‐Gangetic Plain (referred from here as IG LLJ), which we identify as the primary moisture transport mechanism for the northeastern branch of the IAM. We show that the NCAR family of AGCMs (Community Atmospheric Model (CAM)) does not capture this circulation until 1/2° or greater spatial horizontal resolution is used. The IG LLJ develops due to a persistent low‐pressure system centered over the Ganges basin and is enhanced by the Himalayas. Using diabatic heating rates and the moist Froude number as diagnostics, we find that in CAM, this branch of the IAM displays two different dynamical regimes as a function of resolution. At low resolution, the atmosphere near the Himalayas is statically unstable, diabatic heating is strong, and the moisture flow is southwesterly from the Arabian Sea and moves over the terrain (unblocked). At high resolution, the moist static stability near the Himalayan Mountains is stable, diabatic heating is weak, and the flow primarily enters easterly from the Bay of Bengal and moves parallel to the terrain (blocked). During the summer season, the low‐resolution CAM is locked into the unblocked mode, which has serious implications for interpreting topography‐monsoon interactions. For a broader context, we demonstrate that more than half of the CMIP5 models do not capture the IG LLJ, which further highlights model‐data mismatch across the IAM region.

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“…Typically, there is also a well-defined diurnal variation in this region. Precipitation occurs during the afternoon and early morning over the southern plain in Bangladesh (Ohsawa et al 2001;Islam et al 2004;Terao et al 2008), whereas the southerly monsoon flow and low-level jet tend to generate nocturnal precipitation over the northern mountainous areas (Barros and Lang 2003;Kataoka and Satomura 2005;Terao et al 2006;Murata et al 2008;Sato 2013). These seasonal differences in precipitation over South Asia, together with the remarkable diurnal variations, allow us to evaluate the impact of CPs on precipitation simulations.…”

Section: Introductionmentioning

confidence: 99%

Effect of Spatial Resolution and Cumulus Parameterization on Simulated Precipitation over South Asia

Sugimoto

Takahashi

2016

SOLA

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This paper evaluates the ability of a regional-scale climate model to simulate precipitation over the South Asian tropical region. Experiments were conducted using three different spatial resolutions, with and without cumulus parameterization (CP), to assess the influence of horizontal mesh size and the CP on regional-scale precipitation. The experiments that used a finer mesh size but no CP improved the spatial distribution of monthly precipitation relative to that in the experiments based on a coarser spatial resolution. Meanwhile, the impact of horizontal mesh size was much less in the experiments that included the CP because an overestimation of precipitation caused by the CP strongly affected the simulation accuracy in these experiments. Regional differences in diurnal variations in precipitation intensity and frequency were captured reasonably well in the pre-monsoon season regardless of the spatial resolution, and both with and without the CP. In contrast, the diurnal characteristics of precipitation were difficult to simulate during the mature monsoon season. During both seasons, those experiments that incorporated the CP tended to predicted a continuous weak precipitation due to the excessive release of convective instability; accordingly, precipitation intensity was weaker, and precipitation frequency greater than in those experiments that did not use the CP.(Citation: Sugimoto, S., and H. G. Takahashi, 2016: Effect of spatial resolution and cumulus parameterization on simulated precipitation over South Asia. SOLA, 12A, 7−12,

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Monitoring the Monsoon in the Himalayas: Observations in Central Nepal, June 2001

Cited by 182 publications

References 30 publications

Rising Precipitation Extremes across Nepal

Rising Precipitation Extremes across Nepal

The neglected Indo‐Gangetic Plains low‐level jet and its importance for moisture transport and precipitation during the peak summer monsoon

Effect of Spatial Resolution and Cumulus Parameterization on Simulated Precipitation over South Asia

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