Development of a Peltier-based chilled-mirror hygrometer and cloud particle counter for balloon-borne TTL observations
Abstract
Dehydration processes in the TTL determines the amount of water vapor entering the stratosphere. 'In-situ' measurements of water vapor and cloud particles in the TTL are still a technical challenge, and the observational evidence of dehydration is still limited. Accumulation of the observational data is thus necessary to improve the understanding of the TTL dehydration and transport processes. In this study, we have developed a hygrometer and cloud particle counter for balloon-born TTL observations. A Peltier-based digitally-controlled chilled-mirror hygrometer has been developed to measure atmospheric water vapor accurately. The developed sensor is environmentally-friendly and ease-to-handle in nature because this sensor does not use a cryogenic material to cool the mirror. In January of 2012 and 2013, we have conducted some flight tests at Biak, Indonesia (1.18°S, 136.11°E) under the Soundings of Ozone and Water in the Equatorial Region (SOWER) project to evaluate the performances of this sensor. The results of simultaneous measurements with the Cryogenic Frostpoint Hygrometer (CFH) showed that the frost point temperature from the developed sensor is consistent with that from CFH within ~0.5 K in the whole troposphere. In the stratosphere, however, it was found that the controller, which keeps the frost layer on the mirror constant, needs to be further improved. A cloud particle counter has also been developed to measure cloud-particle number density, size distribution, and the particle phase (i.e. liquid water or ice). It is a low-cost and light-weighted (~200 g) particle counter based on a pollen sensor to be used in an air purifier. This sensor consists of a light-emitting part (linearly-polarized light by laser diode) and two light-receiving parts (one detects scattering light directly, while the other detects scattering lights through a polarization plate to estimate the degree of polarization by particles). It is considered that the counts, magnitude of the scattered signals, and the degree of polarization correspond to the particle number density, size, and the phase, respectively. We have conducted some test flights in Japan and in Indonesia between November 2012 and April 2013. The results showed that this sensor can detect cirrus clouds (ice particles) in the TTL and lower tropospheric clouds (liquid water droplets), and discriminate the phase of the particle. However, there are still some problems concerning the measurements of particle size and number density. We need further adjustments of the optical detector part to measure the wide range of number density that the sensor encounters during a tropospheric flight, and further calibration by laboratory experiments to estimate the particle size from the magnitude of the detected signals.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2013
- Bibcode:
- 2013AGUFM.A53M..04S
- Keywords:
-
- 0394 ATMOSPHERIC COMPOSITION AND STRUCTURE Instruments and techniques