Laserfiche WebLink
<br />208 <br /> <br />JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY <br /> <br />VOLUME 4 <br /> <br /> <br /> 0.75 <br />~ <br />6 <br />IY <br />W <br />f--- <br />~ 050 <br />0 <br />:3 <br />a <br />:J <br />IY <br />OJ <br />(J) <br />:::J <br /> 025 <br /> <br />1.00 <br /> <br />0.25 <br /> <br />0.50 <br /> <br />I <br />"1 <br /> <br />~Ql"" Coef . 0.988 <br />Averotje Ilm"te d;ff. . .Ql5rrm <br />Number of ~~"!" 665 <br /> <br />r,,~t"Ceft~~~rtd904 <br />~O.\~B <br /> <br />NOAA LIQUID WATER (mm) <br /> <br />0.75 <br /> <br />1.00 <br /> <br />FIG. 3. Scatter plot of integrated liquid water as measured by the NOAA and USBR radiometers <br />from data taken at Steamboat Springs, CO. Liquid water measurements less than 0.02 mm are <br />not included in this analysis. . <br /> <br />and 101 0, rotating clockwise. The remaining angles <br />could not be scanned simultaneously due to the posi- <br />tion of the cable stops on the scanning drive mechanism <br />caused by the perpendicular orientation of the radi- <br />ometer trailers. <br />Due to the physical separation of the trailers, coor- <br />dination required some skill on the part of the opera- <br />tors. As a result, the degree of coordination on each of <br />the six individual scans varied. The coordination se- <br />quence for each scan is shown on Fig. 4. On the first, <br />the USBR radiometer led the NOAA radiometer by <br />1.5 min. On the second, the USBR radiometer led <br />NOAA by 4 min. On the remaining four scans, near <br />perfect coordination was achieved. Despite coordina- <br />tion problems associated with the first two scans, these <br />scans were included in the data analysis. <br />During the scan sequence, the radiometers average <br />liquid and vapor values over a small range of azimuths <br /> <br />(......2.50). The average over this range is calculated and <br />assigned to the center azimuth of the range. Because <br />of slight variations in the scan rate, the centers of the <br />range for each radiometer do not coincide. Linear in- <br />terpolations between successive data points were used <br />to estimate the values of liquid water and vapor for <br />each radiometer at each integer azimuth (in degrees), <br />and the data for each integer azimuth angle. were then <br />compared. <br />Figure 5 shows the vapor measurements collected <br />by each radiometer as a function of azimuth angle for <br />the six scans. Figure 6 shows similar plots for the liquid <br />water measurements. <br />On the first scan, vapor measurements from both <br />radiometers followed closely with a slight bias in the <br />northern quadrant (USBR greater) and southern <br />quadrant (NOAA greater). The liquid water values were <br />the system noise level (...... :to.03 mm) throughout the <br /> <br />TABLE 1. Comparison of measurements by two radiometers in vertical modes. <br /> <br />Vapor <br />SLW> 0.05 <br /> <br />Vapor <br />SLW < 0.05 <br /> <br />Liquid <br />all points <br /> <br />Vapor , <br />all points <br /> <br />Correlation coefficient <br />Absolute average differential <br />Root mean square differential <br />Number of pairs <br />Slope <br />Intercept <br />Mean (NOAA) <br />Mean (BOR) <br /> <br />0.79 <br />0.07 <br />0.08 <br />77 <br />0.85 <br />0.06 <br />0.66 <br />0.62 <br /> <br />0.95 <br />0.05 <br />0.07 <br />734 <br />0.87 <br />0.04 <br />0.44 <br />0.44 <br /> <br />0.95 <br />0.05 <br />0.07 <br />81\ <br />0.87 <br />0.05 <br />0.46 <br />0.45 <br /> <br />0.99 <br />0.02 <br />0.02 <br />665 <br />0.96 <br />0.00 <br />0.\5 <br />0.\5 <br />