Planetary wave dynamics of the stratosphere, mesosphere and lower thermosphere

Abstract

The wave dynamics of the stratosphere, Mesosphere and Lower Thermosphere (MLT) have been globally investigated using a range of instruments. Theses studies presented here used meteor radars at Esrange, Sweden in the Arctic (68◦N 21◦E), Bear Lake Observatory (BLO), Utah in the USA (42◦N 111◦W) and Rothera, in Antarctica (68◦S 68◦W) to observe the winds and temperatures in the MLT. Further studies used the NASA EOS Aura satellite Microwave Limb Sounder (MLS) instrument to observe temperatures in the middle atmosphere.

The 5- and 16-day planetary waves dynamics have been investigated with ground-based radars, satellites and modelling observations and predictions of the winds and temperatures of the middle atmosphere. The instruments have been used for comparisons and to enhance the understanding of the winds and temperatures of the middle atmosphere.

Meteor radars have been used to observe the climatology of the 5-day planetary wave using wind amplitudes over Esrange and Rothera at heights of ∼80–100 km. A clear seasonal cycle was observed in both hemispheres, with summer and winter maxima. Variances were observed to reach 75m2s−2 in the summer and 65m2s−2 in the winter. The 16-day planetary wave dynamics have been observed over Esrange and Rothera using meteor radar measured winds and temperatures at heights between 80–100km. The 16-day wave seasonal cycle revealed the winter- and summer-time wave to reach amplitudes of 15 and 6ms−1. Further, radar temperature and wind observations of the 16-day wave were found to be linearly related.

Aura MLS temperature data have been used to investigate the 16-day planetary wave at heights of ∼10–100km globally. The structure of the wave was revealed to peak in the polar regions at heights of about 30 and 70km. The inter-annual variability of the wave was investigated to explain the unusual occurrence of the summer-time wave. The Quasi-Biennial Oscillation (QBO) and major Sudden Stratospheric Warming (SSW) were considered as possible influence, but with no clear persistence.

Finally, mean winds and temperatures and the 5- and 16-day planetary waves were studied over BLO using a meteor radar and Aura MLS, winds and temperatures, respectively. The variability of the mean winds and temperatures were compared with the URAP and HWM-07 models. The climatologies of the planetary waves were used to observed the wave dynamics of the middle atmosphere over BLO. A clear seasonal cycle was observed and temperatures and winds were found to be linearly related.

Date of Award	1 Dec 2011
Original language	English
Awarding Institution	University of Bath
Supervisor	Nicholas Mitchell (Supervisor)