**4. Providing estimates: robustness of SRT method and weakness of IDW method**

The SRT method was tested against the Inverse Distance Weighted (IDW) method to deter‐ mine the representativeness of estimates obtained (29). The SRT method outperformed the IDW method in complex terrain and complex microclimates. To illustrate this we have taken the data from a national cooperative observer site at Silver Lake Brighton, UT.The elevation at Silver Lake Brighton is 8740 ft. The nearest neighboring station is located at Soldier Sum‐ mit at an elevation of 7486 ft. This data is for the year 2002. Daily estimates for maximum and minimum temperature were obtained for each day by temporarily removing the obser‐ vation from that day and applying both the IDW (eq. 1) and the SRT (eq.2) methodsagainst 15 neighboring stations. The estimations for the SRT method were derived by applying the method (deriving the un-biased estimates) every 24 data.

**Figure 1.** The results of estimating maximum temperature at Silver Lake Brighton, UT for both the IDW and the SRT methods.

Fig. 1 shows the result for maximum temperature at Silver Lake Brighton, Utah. The IDW approach results in a large bias. The best fit line for IDW indicates the estimates are system‐ atically high by over 8 F (8.27); the slope is also greater than one (1.0684). When the best fit line for IDW estimates was forced through zero, the slope was 1.2152. On the other hand the estimates from the SRT indicate almost no bias as evidenced by the best-fit slope (0.9922).

**5.1. Relationship between interval of measurement and QA failures**

Network uses a midnight to midnight observation period.

**Figure 3.** Example time intervals for observations at Mitchell, NE (after 28).

to two observation periods.

Analyses were conducted to prepare artificial max and min temperature records (not the measurements, but the values identified as the max and min from the hourly time series) for different times-of-observation from available hourly time series of measurements. The ob‐ servation time for coop weather stations varies from site-to-site. Here we define the AM sta‐ tion, PM station, and nighttime station according to the time of observation (i.e. morning, afternoon-evening, and midnight respectively). The cooperative network has a higher num‐ ber of PM stations but AM measurements are also common; the Automated Weather Data

Toward a Better Quality Control of Weather Data

http://dx.doi.org/10.5772/51632

11

The daily precipitation accumulates the precipitation for the past 24 hours ending at the time of observation. The precipitation during the time interval may not match the precipi‐ tation from nearby neighboring stations due to event slicing, i.e. precipitation may occur both before and after a station's time of observation. Thus, a single storm can be sliced in‐

The measurements of the maximum and the minimum temperature are the result of making discrete intervals on a continuous variable. The maximum or minimum temperature takes the maximum value or the minimum value of temperature during the specific time interval. Thus the maximum temperature or the minimum temperature is not necessarily the maxi‐ mum or minimum value of a diurnal cycle. Examples of the differences were obtained from three time intervals (see Fig 3) after28)). The hourly measurements of air temperature were retrieved from 1:00 March 11 to 17:00 March 13, 2002 at Mitchell, NE. The times of observa‐ tion are marked. Point *A* shows the minimum air temperature obtained for March 11 for AM stations, and *B* is the maximum temperature obtained for March 13 at the PM stations. The minimum temperature may carry over to the following interval for AM stations and the

For the minimum temperature estimates a similar result was found (Fig. 2). The slope of the best-fit line for the SRT indicates an unbiased (0.9931) while the slope for the IDW estimates indicates a large bias on the order of 20% (slope = 1.1933). The reader should note the SRT unbiased estimators are derived every 24 days (see ) and that applying the SRT only once for the entire period will degrade the results shown (7).

**Figure 2.** The results of estimating minimum temperature at Silver Lake Brighton, UT for both the IDW and the SRT methods.
