Comparison of Sippican Microsonde and Vaisala Radiosonde 70 hPa and 30 hPa Heights
NWS radiosonde network in the mid-atlantic region
IAD = Sterling, VA. Uses a
Vaisala RS80 Radiosonde
WAL = Wallops Is, VA. Uses a Sippican Mark II
Microsonde
MHX = Moorehead City, NC. Uses a Vaisala RS80
radiosonde
Data for this study was obtained from the NOAA Forecast
Systems Laboratory (FSL)
homepage.
IAD, WAL, and MHX are aligned roughly North to South. From the table and graphs shown below, note that the June 70 and 30 hPa heights at Wallops Island are almost always higher than those at Sterling or Moorehead City. However, the December 70hPa heights at Wallops Island are, on average, between Sterling and Moorehead City. At 30 hPa, WAL is only slightly higher than the other stations. The WAL height bias during June probably is caused by solar/IR radiation affecting the temperature measurements. June soundings are taken in during daylight hours, while soundings taken during December are at night. A radiation correction is applied to Vaisala radiosonde temperature data, while no such correction is applied to Microsonde temperature measurements at the present time. Efforts are underway to improve the accuracy of Microsonde temperatures.
Average 70 hPa heights:
|
June 1998 |
IAD |
WAL |
MHX |
|
70 hPa hgt |
18737.6 |
18795.1 |
18737.5 |
|
Dec. 1998 |
IAD |
WAL |
MHX |
|
70 hPa hgt |
18421.3 |
18455.6 |
18487.4 |
Average 30 hPa heights:
|
June 1998 |
IAD |
WAL |
MHX |
|
30 hPa hgt |
24082.7 |
24164.8 |
24040.2 |
|
Dec. 1998 |
IAD |
WAL |
MHX |
|
30 hPa hgt |
23593.7 |
23634.1 |
23610.2 |
Height averages for these pressure levels at 00 and 12UTC observation times are shown in the table and histograms below:
Average 70 and 30 Hpa heights at 00 and 12 UTC:
|
70 hPa |
IAD 00 |
IAD 12 |
WAL 00 |
WAL 12 |
MHX 00 |
MHX 12 |
|
June 98 |
18764.4 |
18715.3 |
18799.5 |
18791.1 |
18761.7 |
18713.3 |
|
Dec 98 |
18447.4 |
18395.2 |
18480.8 |
18431.5 |
18495.2 |
18480.3 |
|
30 hPa |
IAD 00 |
IAD 12 |
WAL 00 |
WAL 12 |
MHX 00 |
MHX 12 |
|
June 98 |
24123.6 |
24048.7 |
24165.2 |
24164.4 |
24086.5 |
24004.6 |
|
Dec 98 |
23636.4 |
23552.7 |
23666.5 |
23601.7 |
23629.2 |
23592.5 |
The high height bias at Wallops Island may be the cause for the relatively high number of temperature levels NCEP rejected (i.e., bad data) from Wallops Island soundings during May through July, 1998 (see the histogram below). Note that station ALY (Albany, NY) also has a high number of rejections. This station also uses the Sippican Microsonde. Station CHH (Chatham, MA) has a high number of rejections, but uses a Sippican VIZ-B2 radiosonde (NCEP does apply a radiation correction to this radiosonde type).
Below is a similar histogram, but for
November, 1998 through January 1999. Note that the % of rejections at
Wallops Island (and ALY) dropped significantly. Soundings during this
time are taken mostly at night where solar radiation on the radiosonde
temperature sensor does not occur. CHH switched to a Vaisala RS-80
radiosonde during June, 1998.
Back to the Upper-air Observations Main Page