Thursday, May 27, 2010

Improved Sondes

Jimmy C. wrote - I wish they would deploy the double rh sensor I have read about with the dropsonde's, where if one rh sensor gets wet the other is used while the wet one gets heated until it is dry.

The AMA sounding is not that bad (i.e. it should be able to be "fixed"), but the LBF sounding looks to have failed above 450 hPa.
A couple of comments - I assume the new dropsondes mentioned above are the Vaisala model that NOAA contracted for last June (a large contract mostly for hurricane study and monitoring). The technology sounds interesting and expensive. I do hope that Vaisala prevails when the NWS replaces the inferior Sippican sondes. I continue to hear that the Sippican humidity sensor will be replaced asap and also that the evaluation process for a complete replacement of the current sonde is already underway. These are just rumors, since there is no official NWS information available (that I am aware of) about most of the problems nor about how the problems will be repaired.
2 - How does one "fix" a sounding when wet-bulbing occurs? We know that the lapse rate of T has gone awry and we can eliminate the extreme, unrealistic lapse rate. However, since wet-bulbing often occurs when the sonde moves from a saturated layer into a layer that is BOTH warmer and drier. Someone modifying the observed bad data can not know what the extent of the warm inversion (the inversion that has been destroyed by the evaporative cooling of the temperature sensor) actually was - therefore, such bad data can not be fixed, but one could make educated guesses as to what conditions might have actually been.

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