Tropical cyclone cloud‐top height and vertical temperature structure detection using GPS radio occultation measurements

Abstract

Abstract The accurate determination of tropical cyclone (TC) cloud‐top height and its vertical thermal structure using the GPS radio occultation (RO) technique is demonstrated in this study. Cloud‐top heights are determined by using the bending angle anomaly and the temperature anomaly profiles during the TC events, and the results are compared to near‐coincident cloud‐top heights determined by Cloud‐Aerosol Lidar with Orthogonal Polarization (CALIOP) measurements. Based on 34 closely located RO‐CALIOP pairs during 2006 to 2009, TC cloud‐top heights from RO are highly correlated with CALIOP ( r = 0.84), with a mean RO‐CALIOP cloud‐top height difference of approximately 500 m and a root‐mean‐square difference near 1 km. GPS RO data also allow analysis of the TC thermal structure, showing warm anomalies in the middle troposphere and cold anomalies in the upper levels, with a strong inversion near cloud top. We further investigate the thermal structure of the TCs from collocated radiosondes, and identify 246 RO‐radiosonde pairs from 2001 to 2009. Radiosonde data confirm the thermal structure identified in GPS RO, with a strong inversion near the inferred cloud top. The mean difference between RO‐derived inversion heights and those from radiosonde temperature profiles is approximately 500 m. Results show that, while cloud‐top height detected from nadir‐viewing satellites can be easily biased by a few kilometers, the biases of RO‐derived cloud‐top height are within ~500 m.