# Presentation: 281250

## COMPARISON OF MEAN AREAL PRECIPITATION ESTIMATES FROM WSR-88D AND HISTORICAL GAGE NETWORKS OVER CHEAT RIVER BASIN, WV

- David Wang, Michael Smith, D.J. Seo
- Hydrology Laboratory
- Office of Hydrological Development
- National Weather Service/NOAA

## Objectives

- Long term goal is to effectively use NEXGEN data for hydrological forecasting;
- Evaluating radar-based MAPX quality over the Cheat River Basin, WV, which is selected as a study basin for Distributed Model Inter-comparison Project (DMIP);

## MAPX Calculation

- Period:	Mar. 1, 1996 - Dec. 31, 1999
- MAPX are calculated using NEXRAD Stage III data, which are archived at Hydrology Laboratory, NWS;
- Stage III HRAP grid are in resolution of  4 X 4 km;

## MAP Calculation

- Period:	Oct. 1, 1952 - Dec. 31, 1999
- Calculated from the National Climatic Data Center (NCDC) archives;
- The domain covered Cheat River Basin has 16 valid hourly gages and 45 daily gages;
- Quality control procedures are applied to various stages of calculation by using Interactive Double Mass Analysis (IDMA);

## MAP Calculation (cont.)

- d

-  Daily value for a station is distributed
- into hourly values based on the nearby
- hourly observations;
-  Missing values are estimated by 1/d^2;
-  MAP are calculated by multiplying pre-
- determined weighting factors  station observed
- precipitation;

## Radar Coverage over Cheat River Basin

## 	3).  Term “unconditional” means MAP>=0 and  MAP>=0.  

- Monthly and annual averaged hourly MAP & MAPX (mm)
- on different conditions over Cheat River Basin

- Note:	1).  Ratio is MAPX/MAP;
- 	2).  Missing values are removed from the calculations;
- 	3).  Term “unconditional” means MAP>=0 and  MAP>=0.

## Slide 8

## Slide 9

## Slide 10

## Slide 11

## Caption:	Red  -- Station WV8986 hourly precipitation;

- Caption:	Red  -- Station WV8986 hourly precipitation;
- 	Pink  -- MAPX time series;
- 	Yellow  -- Corrected MAPX time series;
- 	White -- MAP time series.

## Caption:	Red  -- Station WV8986 hourly precipitation;

- Caption:	Red  -- Station WV8986 hourly precipitation;
- 	Pink  -- MAPX time series;
- 	Yellow  -- Corrected MAPX time series;
- 	White -- MAP time series.

## Caption:	Pink  -- MAPX time series;

- Caption:	Pink  -- MAPX time series;
- 	Yellow  -- Corrected MAPX time series;
- 	White -- MAP time series.

## Caption:	Pink  -- MAPX time series;

- Caption:	Pink  -- MAPX time series;
- 	Yellow  -- Corrected MAPX time series;
- 	White -- MAP time series.

## Caption:	Pink  -- MAPX time series;

- Caption:	Pink  -- MAPX time series;
- 	Yellow  -- Corrected MAPX time series;
- 	White -- MAP time series.

## Caption:	Red  -- Station WV8986 hourly precipitation;

- Caption:	Red  -- Station WV8986 hourly precipitation;
- 	Pink  -- MAPX time series;
- 	Yellow  -- Corrected MAPX time series;
- 	White -- MAP time series.

## Correction of MAPX time series

- Divide MAPX range into 10 section based on the occurrence probability;
- Calculate the correction factor for each section (MAP/MAPX) in cold and warm seaon;
- Apply correction factors to MAPX time series;

## Summary of Results

- Long-term annual MAP is 52.87 in, PRISM annual MAP is 54.15 in,  4-year averaged MAPX is 30.87 in;
- Radar-based MAPX is under-estimated by about 41% with comparison to MAP;
- MAPX time series over Cheat River Basin is usable after correction by multiplying correction factors;