This study investigates the asymmetric distribution of hurricane boundary layer height scales in a storm-motion-relative framework using global positioning system (GPS) dropsonde observations. Data from a total of 1916 dropsondes collected within four times the radius of maximum wind speed of 37 named hurricanes over the Atlantic basin from 1998 to 2015 are analyzed in the composite framework. Motion-relative quadrant mean composite analyses show that both the kinematic and thermodynamic boundary layer height scales tend to increase with increasing radius in all four motion-relative quadrants. It is also found that the thermodynamic mixed layer depth and height of maximum tangential wind speed are within the inflow layer in all motion-relative quadrants. The inflow layer depth and height of the maximum tangential wind are both found to be deeper in the two front quadrants, and they are largest in the right-front quadrant. The difference in the thermodynamic mixed layer depth between the front and back quadrants is smaller than that in the kinematic boundary layer height. The thermodynamic mixed layer is shallowest in the right-rear quadrant, which may be due to the cold wake phenomena. The boundary layer height derived using the critical Richardson number ( $R_{ic}$ ) method shows a similar front-back asymmetry as the kinematic boundary layer height.

The microwave temperature sounder (MWTS) on board the third FengYun satellite (FY‐3C) is well suited for the detection of tropical cyclones because the observed radiance is insignificantly affected by non‐precipitating clouds. In this study, a stepwise multiple linear regression technique is proposed to retrieve the atmospheric temperature profiles based on MWTS measurements. Under clear‐sky conditions, the root‐mean‐square error of retrieved temperature is no >1.4 K, which is low enough to monitor the thermal structure within typhoons. An application of this method to the Super Typhoon Rammasun resolves the warm‐core eye and temperature gradients across the eye‐wall very well.

This study analyses Global Positioning System dropsondes to document the axisymmetric tropical cyclone (TC) boundary-layer structure, based on storm intensity. A total of 2608 dropsondes from 42 named TCs in the Atlantic basin from 1998 to 2017 are used in the composite analyses. The results show that the axisymmetric inflow layer depth, the height of maximum tangential wind speed, and the thermodynamic mixed layer depth are all shallower in more intense TCs. The results also show that more intense TCs tend to have a deep layer of the near-saturated air inside the radius of maximum wind speed (RMW). The magnitude of the radial gradient of equivalent potential temperature (θ_e) near the RMW correlates positively with storm intensity. Above the inflow layer, composite structures of TCs with different intensities all possess a ring of anomalously cool temperatures surrounding the warm-core, with the magnitude of the warm-core anomaly proportional to TC intensity. The boundary layer composites presented here provide a climatology of how axisymmetric TC boundary layer structure changes with intensity.

The third FengYun satellite (FY-3C) was successfully launched into morning-configured orbit on 23 September 2013. The cross-tracking scanning instrument microwave temperature sounder (MWTS) on board FY-3C provides 13 channels, many more than the four MWTS channels on board FY-3A/B, at frequencies ranging from 50 to 60 GHz, which allow for probing the atmospheric temperature under all conditions except heavy precipitation. This study investigates and assesses the quality of the brightness temperature measurements from MWTS using the rapid radiative transfer model. Overall, MWTS observations (labelled ‘O’) compare favourably with simulations (labelled ‘B’) for troposphere and stratosphere channels except for surface-sensitive channels, the measurements of which provide more detail of thermal structures in the lower troposphere, especially for storm conditions such as tropical cyclones. Moreover, measurements from channels 1 and 4 can be used to derive the cloud liquid water path index (LWP_index) for cloud detection. However, this study also finds that (1) the brightness temperature differences (labelled ‘O-B’) between observations and model simulations exhibit a clear striping pattern for upper level channels; (2) the geolocation result has a systematic bias towards the real geolocation; and (3) the calibrated cold space view is contaminated by light reflected from the moon.

This study examines the shear-relative rainfall spatial distribution of tropical cyclones (TCs) during landfall based on the 19-year (1998–2016) TRMM satellite 3B42 rainfall estimate dataset and investigates the role of upper-tropospheric troughs on the rainfall intensity and distribution after TCs make a landfall over the six basins of Atlantic (ATL), eastern and central Pacific (EPA), northwestern Pacific (NWP), northern Indian Ocean (NIO), southern Indian Ocean (SIO), and South Pacific (SPA). The results show that the wavenumber 1 perturbation can contribute ∼ 50% of the total perturbation energy of total TC rainfall. Wavenumber 1 rainfall asymmetry presents the downshear-left maxima in the deep-layer vertical wind shear between 200 and 850 hPa for all the six basins prior to making a landfall. In general, wavenumber 1 rainfall tends to decrease less if there is an interaction between TCs and upper-level troughs located at the upstream of TCs over land. The maximum TC rain rate distributions tend to be located at the downshear-left (downshear) quadrant under the high (low)-potential vorticity conditions.