Extended validation of Aeolus winds with wind-profiling radars in Antarctica and Arctic Sweden

Winds from two wind profiling radars, ESRAD in Arctic Sweden and MARA on the coast of Antarctica, are compared with collocated winds measured by the Doppler lidar onboard the Aeolus satellite for the time period July 2019&ndash;May 2021. Data is considered as a whole, and subdivided into summer/winter and ascending (afternoon) /descending (morning) passes. Mean differences (bias) and random differences are categorised (standard deviation and scaled median absolute deviation) and the effects of different quality criteria applied to the data are assessed, including the introduction of the &lsquo;modified Z-score&rsquo; to eliminate gross errors. This last criterion has a substantial effect on the standard deviation, particularly for Mie winds. Significant bias is found in two cases, for Rayleigh/descending winds at MARA (-1.4 (+0.7) m/s) and for all Mie winds at ESRAD (+1.0 (+0.3) m/s). For the Rayleigh wind bias at MARA, there is no obvious explanation for the bias in the data distribution. For the Mie wind at ESRAD there is a clear problem with a distribution of wind differences which is skewed to positive values (Aeolus HLOS wind &gt; ESRAD wind). Random differences (scaled median absolute deviation) for all data together are 5.9 / 5.3 m/s for Rayleigh winds at MARA/ESRAD respectively , and 4.9 / 3.9 m/s for Mie winds. These represent an upper bound for Aeolus wind random errors since they are due to a combination of spatial differences, and random errors in both radar winds and Aeolus winds.</p

Fine-scale model simulation of gravity waves generated by Basen nunatak in Antarctica

Peer reviewe

Ozone loss derived from balloon-borne tracer measurements and the SLIMCAT CTM

Balloon-borne measurements of CFC-11 (on flights of the DIRAC in situ gas chromatograph and the DESCARTES grab sampler), ClO and O3 were made during the 1999/2000 winter as part of the SOLVE-THESEO 2000 campaign. Here we present the CFC-11 data from nine flights and compare them first with data from other instruments which flew during the campaign and then with the vertical distributions calculated by the SLIMCAT 3-D CTM. We calculate ozone loss inside the Arctic vortex between late January and early March using the relation between CFC-11 and O3 measured on the flights, the peak ozone loss (1200 ppbv) occurs in the 440–470 K region in early March in reasonable agreement with other published empirical estimates. There is also a good agreement between ozone losses derived from three independent balloon tracer data sets used here. The magnitude and vertical distribution of the loss derived from the measurements is in good agreement with the loss calculated from SLIMCAT over Kiruna for the same days

Temperature Variations Seen by High Resolution Radiosondes as Signs of Turbulence, Comparison with ESRAD

Upprättat; 2016; 20160616 (andbra)</p

Unusual Radar Echo from the Wake of Meteor Fireball in Nearly Horizontal Transits in the Summer Polar Lower-Thermosphere

The summer polar lower thermosphere (90-100 km) has an interesting connection to meteors, adjacent to the mesopause region attaining the lowest temperature in summer. Meteors supply condensation nuclei for charged ice particles causing polar mesospheric summer echoes (PMSE). We report the observation of meteor trail with nearly horizontal transit at high speed (20-50 km/s), and at last with re-enhanced echo power followed by diffusive echoes. Changes in phase difference between radar receivers aligned in meridional and zonal directions are used to determine variations in horizontal displacements and speeds with respect to time by taking advantage of radar interferometric analysis. The actual transit of echo target is observed along the straight pathway vertically and horizontally extended as much as a distance of at least 24 km and at most 29 km. The meteor trail initially has a signature similar to `head echoes`, with travel speeds from 20 - 50 km/s. It subsequently transforms into a different type of echo target including specular echo and then finally the power reenhanced. The reenhancement of echo power is followed by fume-like diffusive echoes, indicating sudden release of plasma as like explosive process probably involved. We discuss a possible role of meteor-triggered secondary plasma trail, such as fireball embedded with electrical discharge that continuously varies the power and transit speed