The Monsoon Himalayan Precipitation Experiment (MOHPREX) occurred during June 2001 along the south slopes of the Himalayas in central Nepal. Radiosondes were launched around the clock from two sites, one in the Marsyandi River basin on the eastern footslopes of the Annapurna range, and one farther to the southwest near the border with India. The flights supported rainfall and other hydrometeorological observations (including surface winds) from the Marsyandi network that has been operated in this region since the spring of 1999. The thermodynamic profiles obtained from the soundings support the observed nocturnal maximum in rainfall during the monsoon, with total column moisture and instability maximized just before rainfall peaks. Coinciding with the appearance of a monsoon depression over central India, the onset of the monsoon in this region was characterized by a weeklong weakening of the upper-level westerlies, and an increase in moisture and convective instability. The vertical structure of convection during the project was intense at times, and frequent thunder and lightning were observed. This is suggestive of monsoon break convection, which is expected to be predominant since the monsoon had not fully matured by the end of the month. Comparisons of the MOHPREX data with the NCEP-NCAR reanalysis data reveal that upper-level winds are characterized relatively well by the reanalysis, taking into account the coarse model topography. However, moisture is severely underestimated, leading to significant underestimation of rainfall by the reanalysis. The interaction of the ambient monsoon flow with the south slopes of the Himalayas, modulated by the diurnal variability of atmospheric state, is suggested as the primary cause of the nocturnal peak in rainfall.

The Marsyandi River basin in the central Nepalese Himalayas is a topographically complex region, with strong spatial gradients of precipitation over various timescales. A meteorological network consisting of 20 stations was installed at a variety of elevations (528-4435 m) in this region, and measurements of rainfall were made during the 1999 and 2000 summer monsoons. The onsets of the 1999 and 2000 monsoons in central Nepal were examined at different spatial scales by using a combination of rain gauge, Meteosat-5, Tropical Rainfall Measuring Mission (TRMM), ECMWF analysis, and Indian radiosonde data. At the network, the onsets manifested themselves as multiday rain events, which included a mixture of stratiform and convective precipitation. Moist and unstable upslope flow was associated with the occurrence of heavy rainfall. During each onset, 2day rainfall reached as high as 462 mm, corresponding to 10%-20% of the monsoon rainfall. Differences among rain gauges were up to a factor of 8, reflecting the role of small-scale terrain features in modulating rainfall amounts. At the larger scale, the onsets were associated with monsoon depressions from the Bay of Bengal that moved close enough to the Himalayas to cause the observed upslope flow from the winds on their eastern flank. During the 1999 onset, convection in this eastern flank collided with the mountains in the vicinity of the network. In 2000 no major collision occurred, and 33%-50% less rain than 1999 fell. Analysis of observations for a 5yr period (1997-2001) suggests that the interannual variability of the monsoon onset along the Himalayan range is linked to the trajectories and strength of these depressions.

Probable maximum precipitation (PMP) is the conceptual construct that defines the magnitude of extreme storms used in the design of dams and reservoirs. In this study, the value and utility of applying multifractal analysis techniques to systematically calculate physically meaningful estimates of maximum precipitation from observations in the eastern United States is assessed. The multifractal approach is advantageous because it provides a formal framework to infer the magnitude of extreme events independent of empirical adjustments, which is called the fractal maximum precipitation (FMP), as well as an objective estimate of the associated risk. Specifically, multifractal (multiscaling) behavior of maximum accumulated precipitation at daily (327 rain gauges) and monthly (1400 rain gauges) timescales, as well as maximum accumulated 6-hourly precipitable water fluxes for the period from 1950 to 1997 were characterized. Return periods for the 3-day FMP estimates in this study ranged from 5300 to 6200 yr. The multifractal parameters were used to infer the magnitude of extreme precipitation consistent with engineering design criterion (e.g., return periods of 10 6 yr), the design probable maximum precipitation (DPMP). The FMP and DPMP were compared against PMP estimates for small dams in Pennsylvania using the standard methodology in engineering practice (e.g., National Weather Service Hydrometeorological Reports 51 and 52). The FMP estimates were usually, but not always, found to be lower than the standard PMP (FMP/PMP ratios ranged from 0.5 to 1.0). Furthermore, a high degree of spatial variability in these ratios points to the importance of orographic effects locally, and the need for place-based FMP estimates. DMP/PMP ratios were usually greater than one (0.96 to 2.0), thus suggesting that DPMP estimates can provide a bound of known risk to the standard PMP.

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SummaryGround validation (GV) campaigns before and after the launch of NASA's Global Precipitation Measurement Mission (GPM) Core satellite in early 2014 have been planned to collect targeted observations to support precipitation retrieval algorithm development, to improve the science of precipitation processes, and to demonstrate the utility of GPM data for operational hydrology and water resources applications. The Integrated Precipitation and Hydrology Experiment (IPHEx) centered in the Southern Appalachians and spanning into the Piedmont and Coastal Plain regions of North Carolina seeks to characterize warm season orographic precipitation regimes, and the relationship between precipitation regimes and hydrologic processes in regions of complex terrain.Since 2007, a high elevation tipping bucket rain gauge network has been in place in the Pigeon River Basin (PRB) in the Southern Appalachians and intensive observing periods (IOPs) have been conducted in this and surrounding river basins to characterize ridgeridge and ridge-valley variability of precipitation using radiosondes, tethersondes, MicroRain Radars (MRRs), automatic weather stations and optical disdrometers. Important results from these analyses include the importance of light (<3 mm/hr) rainfall as a baseline freshwater input to the region especially in the cold season, and the high frequency of heavy rainfall and severe weather in the warm season, and illuminate the significant spatio-temporal variability of rainfall in this region.IPHEX will consist of two activities: 1) an extended observing period (EOP) from October 2013 through October 2014 including a science-grade raingauge network of 60 stations, half of which will be equipped with multiple raingauge platforms, in addition to the fixed regional observing system; a disdrometer network consisting of twenty separate clusters; and two mobile profiling facilities including MRRs; and 2) an intense observing period (IOP) from May-July of 2014 post GPM launch focusing on 4D mapping of precipitation structure during which NASA's NPOL S-band scanning dual-polarization radar, the dual-frequency Ka-Ku, dual polarimetric, Doppler radar (D3R), four additional MRRs, and the NOAA NOXP radar ) will be deployed in addition to the long-term fixed instrumentation. During the IOP, the NASA ER-2 and the UND Citation aircraft will be used to conduct high altitude and "in the column" measurements.The ER-2 will be equipped with multi-frequency-radiometers (AMPR and CoSMIR), the dual-frequency Ka-Ku band, HIWRAP Ka-Ku band, CRS W-band, and EXRAD X-band radars. The ER-2 instrument complement collectively functions as an expanded GPM Core "satellite proxy". The UND Citation instruments will be dedicated to microphysical 3 characterization. The ground-based instrumentation sites were selected to collect extensive samples of orographic effects on microphysical properties of precipitation, specifically DSDs, for the dominant warm season precipitation regimes in the region: 1) westerly systems including Mesoscale Convective...