A method to determine true air temperature fluctuations in clouds with liquid water fraction and estimate water droplet effect on the calculations of the spectral structure of turbulent heat fluxes in cumulus clouds based on aircraft data

- We made a specialized wind tunnel (SWT) with an air flow speed up to 80 ms− 1 in the testing section.
- We made an air flow with liquid water fraction similar to that in a cumulus cloud in the testing section.
- We investigated liquid water droplet effect on temperature measurements.
- We estimated water content correcting coefficient for the aircraft thermometer.
- We estimated liquid water effect on the spectral structure of the fields of air temperature and heat fluxes in a cumulus zone.

Liquid water droplets could distort aircraft temperature measurements in clouds, leading to errors in calculated heat fluxes and incorrect flux distribution pattern. The estimation of cloud droplet effect on the readings of the high-frequency aircraft thermometer employed at the Central Aerological Observatory (CAO) was based on an experimental study of the sensor in a wind tunnel, using an air flow containing liquid water droplets. Simultaneously, calculations of the distribution of speed and temperature in a flow through the sensitive element of the sensor were fulfilled. This permitted estimating the coefficient of water content effect on temperature readings. Another way of estimating cloud droplet effect was based on the analysis of data obtained during aircraft observations of cumulus clouds in a tropical zone (Cuba Island). As a result, a method of correcting air temperature and recovering true air temperature fluctuations inside clouds was developed. This method has provided consistent patterns of heat flux distribution in a cumulus area. Analysis of the results of aircraft observations of cumulus clouds with temperature correction fulfilled has permitted investigation of the spectral structure of the fields of air temperature and heat fluxes to be performed in cumulus zones based on wavelet transformation. It is shown that mesoscale eddies (over 500 m in length) were the main factor of heat exchange between a cloud and the ambient space. The role of turbulence only consisted in mixing inside the cloud.