Observed seasonal to decadal scale responses in mesospheric water vapor

Abstract

[1] The 14 year (1991)(1992)(1993)(1994)(1995)(1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005) time series of mesospheric water vapor from the Halogen Occultation Experiment (HALOE) are analyzed using multiple linear regression (MLR) techniques for their seasonal and longer-period terms from 45°S to 45°N. The distribution of annual average water vapor shows a decrease from a maximum of 6.5 ppmv at 0.2 hPa to about 3.2 ppmv at 0.01 hPa, in accord with the effects of the photolysis of water vapor due to the Lyman-a flux. The distribution of the semiannual cycle amplitudes is nearly hemispherically symmetric at the low latitudes, while that of the annual cycles shows larger amplitudes in the Northern Hemisphere. The diagnosed 11 year, or solar cycle, max minus min, water vapor values are of the order of several percent at 0.2 hPa to about 23% at 0.01 hPa. The solar cycle terms have larger values in the Northern than in the Southern Hemisphere, particularly in the middle mesosphere, and the associated linear trend terms are anomalously large in the same region. Those anomalies are due, at least in part, to the fact that the amplitudes of the seasonal cycles were varying at northern midlatitudes during 1991-2005, while the corresponding seasonal terms of the MLR model do not allow for that possibility. Although the 11 year variation in water vapor is essentially hemispherically symmetric and antiphased with the solar cycle flux near 0.01 hPa, the concurrent temperature variations produce slightly colder conditions at the northern high latitudes at solar minimum. It is concluded that this temperature difference is most likely the reason for the greater occurrence of polar mesospheric clouds at the northern versus the southern high latitudes at solar minimum during the HALOE time period.

Methane as a diagnostic tracer of changes in the Brewer–Dobson circulation of the stratosphere

“…Results of similar MLR analyses of time series of HALOE data were reported for ozone (Remsberg, 2008), temperature (Remsberg, 2009), and mesospheric water vapor (Remsberg, 2010). Details of the formulation of the terms for the MLR models can be found in Remsberg (2008) and are summarized here.…”

Aura Microwave Limb Sounder observations of the polar middle atmosphere: Dynamics and transport of CO and H2O

“…Variances explained by the HSAM are larger in the middle and lower stratosphere than those of HNAM, consistent with larger planetary wave amplitudes in the NH stratosphere. The variance explained by the first mode of H 2 O is less than that from GPH, possibly due in part to local variability caused by the interplay between chemistry and dynamics [e.g., Flury et al , 2008; Remsberg , 2010].…”

Signature of the 27-day solar rotation cycle in mesospheric OH and H<sub>2</sub>O observed by the Aura Microwave Limb Sounder

“…The response of OH from Fritz Peak Observatory (Colorado) to 11-yr solar cycle was reported by Canty and Minschwaner (2002). The H 2 O response obtained from HALOE (HALogen Occultation Experiment) between 1991 and 2005 to the 11-yr solar cycle was found to be strong ("max minus min" H 2 O response is about 23 % at 0.01 hPa) and negative (Remsberg, 2010). However, the responses to the 27-day solar rrotational cycle were not yet found.…”