Search Results

You are looking at 1 - 3 of 3 items for :

  • Author or Editor: Justin R. Minder x
  • Journal of Hydrometeorology x
  • Refine by Access: All Content x
Clear All Modify Search
Alison M. Anders
,
Gerard H. Roe
,
Dale R. Durran
, and
Justin R. Minder

Abstract

Persistent, 10-km-scale gradients in climatological precipitation tied to topography are documented with a finescale rain and snow gauge network in the Matheny Ridge area of the Olympic Mountains of Washington State. Precipitation totals are 50% higher on top of an ∼800-m-high ridge relative to valleys on either side, 10 km distant. Operational fifth-generation Pennsylvania State University–NCAR Mesoscale Model (MM5) runs on a 4-km grid produce similar precipitation patterns with enhanced precipitation over high topography for 6 water years.

The performance of the MM5 is compared to the gauge data for 3 wet seasons and for 10 large precipitation events. The cumulative MM5 precipitation forecasts for all seasons and for the sum of all 10 large events compare well with the precipitation measured by the gauges, although some of the individual events are significantly over- or underforecast. This suggests that the MM5 is reproducing the precipitation climatology in the vicinity of the gauges, but that errors for individual events may arise due to inaccurate specification of the incident flow.

A computationally simple model of orographic precipitation is shown to reproduce the major features of the event precipitation pattern on the windward side of the range. This simple model can be coupled to landscape evolution models to examine the impact of long-term spatial variability in precipitation on the evolution of topography over thousands to millions of years.

Full access
Jessica D. Lundquist
,
Justin R. Minder
,
Paul J. Neiman
, and
Ellen Sukovich

Abstract

The rate of precipitation increase with elevation, termed the orographic precipitation gradient (OPG), is critically important for hydrologic forecasting in mountain basins that receive both rain and snow. Here, the following are examined to see how well they are able to predict the OPG and how it changes between storms and years: 1) a linear model of orographic precipitation forced by upstream radiosonde data, 2) monthly Parameter-Elevation Regressions on Independent Slopes Model (PRISM) precipitation data, and 3) seven years of hourly wind profiler data used to identify characteristics of the Sierra barrier jet (SBJ). These are compared against 124 daily resolution (four of which also had quality controlled, hourly resolution) precipitation gauge records in the northern Sierra Nevada. All methods represent the OPG well in the mean and during a year when less than 30% of the precipitation occurred on days with SBJs. However, the linear model and PRISM do not adequately capture annual variations in the OPG during years when more than 70% of the precipitation occurred on days with SBJs. Throughout all of the years, wind profiler data indicating the height of the SBJ provided additional, and necessary, information. The OPG is negatively correlated with the height of the SBJ. The SBJ height is lower, and hence, the OPG greater when the westerly winds are stronger, with more vertical wind shear. These westerly storms result in greater increases of precipitation with elevation, which act to increase snow storage in most storms but also to increase storm runoff during warmer-than-average storms.

Full access
Adam K. Massmann
,
Justin R. Minder
,
René D. Garreaud
,
David E. Kingsmill
,
Raul A. Valenzuela
,
Aldo Montecinos
,
Sara Lynn Fults
, and
Jefferson R. Snider

Abstract

The Chilean Coastal Orographic Precipitation Experiment (CCOPE) was conducted during the austral winter of 2015 (May–August) in the Nahuelbuta Mountains (peak elevation 1.3 km MSL) of southern Chile (38°S). CCOPE used soundings, two profiling Micro Rain Radars, a Parsivel disdrometer, and a rain gauge network to characterize warm and ice-initiated rain regimes and explore their consequences for orographic precipitation. Thirty-three percent of foothill rainfall fell during warm rain periods, while 50% of rainfall fell during ice-initiated periods. Warm rain drop size distributions were characterized by many more and relatively smaller drops than ice-initiated drop size distributions. Both the portion and properties of warm and ice-initiated rainfall compare favorably with observations of coastal mountain rainfall at a similar latitude in California. Orographic enhancement is consistently strong for rain of both types, suggesting that seeding from ice aloft is not a requisite for large orographic enhancement. While the data suggest that orographic enhancement may be greater during warm rain regimes, the difference in orographic enhancement between regimes is not significant. Sounding launches indicate that differences in orographic enhancement are not easily explainable by differences in low-level moisture flux or nondimensional mountain height between the regimes.

Full access