H-SAF Product Validation Report (PVR) PR-OBS-3

More documents

Recommendations

Info

Products Validation Report, 30 May 2010 - PVR-03 (Product PR-OBS-3) Page 36 Validation of precipitation products is based mainly on the comparison with the AWOS and weather radar data measurements. Turkey has an extensive coverage of meteorological observations, including automated weather observing stations (AWOS), synoptic and climatological stations, and 4 radars. At present nearly 450 meteorological, 60 airport, 180 climate, and 7 upper air (radiosonde) stations are in operation. The meteorological observation network has been strengthened by installation of AWOS in recent years, and in the near future almost entire country will be covered by an AWOS network to replace the conventional network. As shown in Fig. 26, the Western Black Sea catchment has 23 AWOS and 7 synoptic stations in addition to radar coverage. Similarly, the Susurluk basin has 17 AWOS and 3 synoptic stations and radar coverage. Fig. 26 - Network of Meteorological stations in Susurluk (on the left) and Western Black Sea (on the right) catchments. Starting from January 2009, the validation area has been extended to the middle and western Turkey. 193 Automated Weather Observation Station (AWOS) located in the western part of Turkey are used for the validation of the precipitation products. The locations of the AWOS sites are shown in Fig. 27. Fig. 27 - Position of 193 AWOS sites used for ground truth for the precipitation product validation in western Turkey. Validation Methodology Due to the time and space structure of precipitation and sampling characteristics of both the precipitation products and observations used for validation, care has to be taken to bring data to a comparable level. At a given place, precipitation occurs intermittently and at highly fluctuating rates. Over space, precipitation is distributed with a high variability, in cells of high intensity nested in larger area with lower rain rate. Aimed at observing this complex phenomenon, the satellite-based products are defined with a spatial resolution of several kilometres and with different sampling rate and accumulation
Products Validation Report, 30 May 2010 - PVR-03 (Product PR-OBS-3) Page 37 time. On the other hand, reference observations against which the products are going to be validated are also characterized by their own spatial resolution ranging from point information measured on raingauge networks to grids with cells of several hundreds of meters to several kilometres for weather radar. Furthermore, none of these reference observations are without error. Each precipitation product within the H-SAF project represents a foot print geometry. Among these, H01 and H02 products represent an elliptical geometry while H03 and H05 have a rectangular geometry. On the other hand, the ground observation (rain-gauge) network consists of point observations. The main problem in the precipitation product cal/val activities occurs in the dimension disagreement between the product space (area) and the ground observation space (point). To be able to compare both cases, either area to point (product to site) or point to area (site to product) procedure has to be defined. However, the first alternative seems easier. The basic assumption in such an approach is that the product value is homogenous within the product footprint. Fig. 28 presents satellite foot print (IFOV) centres of the H02 product, an elliptical footprint for the corresponding centre (area within the yellow dots) and AWOS ground observation sites. The comparison statistic can be performed by considering just the sites in the footprint area. Although this approach is reasonable on the average but it is less useful in spatial precipitation variability representation. The comparison is not possible when no site is available within the footprint area. Fig. 28 - H02 product footprint centres with a sample footprint area as well as the AWOS ground observation sites. Alternatively, the point to area approach is more appealing for the realistic comparison of the precipitation product and the ground observation. This approach is simply based on the determination of the true precipitation field underneath the product footprint area. To do so, the footprint area is meshed and precipitation amounts are estimated at each grid point by using the precipitation observations at the neighbouring AWOS sites as shown in Fig. 29. A 3x3 km grid spacing is considered for the products with elliptical geometry while 2x2 km spacing is considered for the products with rectangular geometry. At each grid point, the precipitation amount is estimated by, Z m n i 1 n W ( r i 1 i, m W ( r ) Z i, m ) i where Z m is the estimated value and W(r i,m ) is the spatially varying weighting function between the i-th site and the grid point m. (1)
Page 1 and 2: Products Validation Report, 30 May
Page 35: Products Validation Report, 30 May
Page 51 and 52: Jan'09 Jan'09 Feb'09 Feb'09 Mar'09
Page 53 and 54: Mean Error [mm/h] Mean Error [mm/h]
Page 87 and 88:
Products Validation Report, 30 May
Page 89 and 90:
Page 91 and 92:
Page 93 and 94:
Page 95 and 96:
Page 97 and 98:
Page 99 and 100:
Page 101 and 102:
Page 103 and 104:
Page 105 and 106:
Page 107 and 108:
Page 109 and 110:
Page 111 and 112:
Page 113 and 114:
Page 115 and 116:
Page 117 and 118:
Page 119 and 120:
Precentage contribution Products Va
Page 121 and 122:
Page 123 and 124:
Page 125 and 126:
Page 127 and 128:
Page 129 and 130:
Page 131 and 132:
Rain Rate (H-03-RG) [mm/h] Dec'07 J
Page 133 and 134:
Page 135 and 136:
GEO/IR+LEO/MW Products Validation R
Page 137 and 138:
percentage of pixels (log) Products
Page 139 and 140:
Page 141 and 142:
Page 143 and 144:
Page 145 and 146:
Page 147 and 148:
Page 149:
show all

H-SAF Product Validation Report (PVR) PR-OBS-3

Create successful ePaper yourself

Delete template?

Save as template?