Observation and Attribution of Temperature Trends Near the Stratopause From HALOE

Abstract

This study considers time series of temperature versus pressure, T(p), from the Halogen Occultation Experiment (HALOE) across the stratopause region, where the effects of radiative forcings from the greenhouse gases (CO2 and H2O) and from ozone are most pronounced. Trend analyses of HALOE T(p) values for 1993–2005 are for six levels from 2.0 to 0.3 hPa with a vertical resolution of about 4 km and for eight latitude zones from 65°S to 65°N. The analyses account for the forcing effects from the 11‐yr solar cycle. HALOE trends at 2.0 hPa are of the order of −1.0 K/decade across the tropics and subtropics but then become smaller (−0.5 K/decade) at the middle latitudes. Near‐global T(p) trends are of order −0.5 K/decade but have a minimum of −0.2 K/decade at 1.0 hPa; they are clearly negative in the southern but slightly positive in the northern hemisphere. The combined radiative forcings from CO2, H2O, and ozone vary between −0.4 and −0.7 K/decade for 1993–2005 and are hemispherically symmetric. The HALOE temperature trend and total radiative cooling profiles differ from those reported from observations and calculations for 1980–2000, mainly because the ozone trends changed from clearly negative in the 1980s through mid‐1990s to slightly positive during the time of HALOE. Trends at low latitudes for the tracer, methane (CH4), increase from 2% to 4%/decade from 50 to 10 hPa and then to ~6%/decade by 5 hPa. Analyses of time series of CH4 across the stratopause reveal subseasonal scale variability within the northern hemisphere that reduces the significance of the T(p) trends.

Long-Term Evolution in Noctilucent Clouds’ Response to the Solar Cycle: A Model-Based Study

“…Observations from the Solar Occultation For Ice Experiment (SOFIE) onboard NASA's Aeronomy of Ice in the Mesosphere (AIM) satellite (Figure 6d in [35]) show that the H 2 O mixing ratio has been around four parts per million volume (ppmv) in recent years, which is in agreement with MIMAS as shown in Figure 1c (run A) in [9]. The recent study by [36] suggests a water vapour trend of about 5% per decade at 52.5 • N and 80 km, corresponding to 0.175 ppmv per decade. This trend is consistent with trends calculated in MIMAS, which show a rate of 0.15 ppmv per decade (see Figure 1c in [9]).…”

Zonal Asymmetry of the Stratopause in the 2019/2020 Arctic Winter

“…The descent of the polar stratopause after it reforms at high altitude is accompanied by the enhanced downward transport and increase in the concentrations of the upper-stratospheric minor species, such as CO and NO, that have sources in the mesosphere [25][26][27][28][29]. Remsberg [30] analyzed the relationship between H 2 O and ozone and the temperature of the stratopause and noted that the increases in H 2 O and decreases in O 3 cool the upper stratosphere.…”

Zonal Asymmetry of the Stratopause in the 2019/2020 Arctic Winter

“…The descent of the polar stratopause after it reforms at high altitude is accompanied by the enhanced downward transport and increase in the concentrations of the upper-stratospheric minor species, such as CO and NO, that have sources in the mesosphere [25][26][27][28][29]. Remsberg [30] analyzed the relationship between H2O and ozone and the temperature of the stratopause and noted that the increases in H2O and decreases in O3 cool the upper stratosphere.…”