Role of water from the ground to the upper atmosphere
12/11 – Thrusday
14:30 - 14:35 Various aspects of the role of water from the ground to the upper atmosphere in the terrestrial atmosphere (Takuji Nakamura )
14:35 - 14:55 Precipitable Water and rainfall variabilites over the Amazon Basin region using the GPS Radio Occultation data, Tropical Rainfall Measuring Mission data and station data (Pablo Llamedo)
The Amazon basin (AB) region (0-20S and 75W-45W), constitutes the largest extent of
tropical rainforest on Earth. The annual mean regional precipitation becomes the most important heat source for the tropical atmosphere providing almost 15 % of the global water discharged to the oceans.
The precipitable water content (PW) and specific humidity (q) obtained by the Global Positioning System (GPS) Radio Occultation (RO) technique (2006-2014), daily accumulated rainfall data (3B42 v7 product) obtained by the Tropical Rainfall Measuring Mission (TRMM) (1998-2013) and daily rainfall station data (Brazilian water agency) were used to study the variabilities in climate signal over the AB.
A multivariate linear regression is applied to time series to study the deppendace of longer signals like ENSO and possible trends. The correlations between PW and rainfall is analized. Also, a continuous wavelet transform is applied to PW and rainfall to investigate the temporal and spatial modes of oscullation.
14:55 - 15:15 Dynamical processes and transport influencing the water vapour budget in the upper troposphere / lower stratosphere (UTLS) (Martin Riese)
Changes and variability of UTLS composition are major drivers of surface climate change (e.g. Solomon et al., 2010). Even small changes of spatially highly variable concentrations of greenhouse gases such as water vapor (H2O) have significant effects on the atmospheric radiation balance. Improved projections of chemistry-climate models (CCM) therefore rely on a realistic representation of physical and chemical processes affecting UTLS composition. This is problematic, because UTLS composition is governed by the complex interactions of various physical and chemical processes that operate at a wide range of temporal and spatial scales (local to global).
We analyze important underlying processes based on multi-annual simulations by the Chemical Lagrangian Model of the Stratosphere (CLaMS), in combination with satellite observations. Our results indicate that the Asian monsoon plays a crucial role for transporting moist air from the tropical troposphere into the extra-tropical lowermost stratosphere during boreal summer. In the tropics, transport of water vapour into the deep stratosphere, which is associated with the ascending branch of the large-scale Brewer-Dobson circulation, is significantly influenced by the Quasi Biennial Oscillation and by Major Stratospheric Warming events during boreal winter.
15:15 - 15:45 Dehydration processes inside the Antarctic polar vortex (Yoshihiro Tomikawa)
Interannual variations of stratospheric water vapor have a large impact on the surface temperature as well as the stratospheric temperature. The stratospheric water vapor concentration is primarily controlled by dehydration processes in the tropical tropopause layer and methane oxidation in the stratosphere. However, the water vapor concentration inside the stratospheric polar vortex, especially in the Antarctic, is affected by additional dehydration, because the lower stratosphere in the polar vortex becomes colder than the tropical tropopause. Thus it is inferred that the stratospheric water vapor, which is one of primary greenhouse gases, over the Antarctic changes in a different way from other latitude regions. In order to examine how much the stratospheric water vapor concentration varies due to the dehydration and any other processes unique to the Antarctic stratosphere, a trajectory-based analysis is applied to the stratospheric water vapor data of the Microwave Limb Sounder (MLS) onboard the Aura satellite. It can give a minimum saturation mixing ratio of water vapor on each trajectory, which should be identical with the observed water vapor mixing ratio if it is determined by the dehydration during the trajectory period. This analysis will provide quantitative estimates of the dehydration and any other processes contributing to the variation of water vapor concentration in the Antarctic stratosphere.
15:45 - 16:05 Water vapour and ion chemistry in the mesosphere and lower thermosphere - a model study (Holger Winkler)
The ion chemistry of the Earth’s mesosphere and lower thermosphere (MLT) region is affected by the concentration of water vapour. In particular, the height-distribution of proton hydrates (PHs) and non-proton hydrates (NPHs) depends on the water profile. Due to the fact that PHs and NHPs as well as molecular ions possess different reactivities, the ion composition of the D-region is linked to water. We present model simulations of hydrogen species and ions in the MLT region. For this purpose, a detailed ion-chemistry model is used in combination with a one-dimensional atmospheric chemistry and diffusion model. Additionally, water profiles from satellite observations are considered. The model is applied to quiet ionospheric conditions as well as to solar particle events.
17:00 - 17:30 Trends in Mesospheric Ice Layers in the Northern Hemisphere during 1961-2013 (Uwe Berger)
17:30 - 18:00 Observations of Polar Mesospheric Clouds from Space and Their Scientific Implications (Scott Bailey)
Observations of Polar Mesospheric Clouds (PMCs), also called Noctilucent Clouds, were first reported in 1885 by the amateur astronomer Robert Leslie. Since that time there has been a growing public and scientific interest in these beautiful, iridescent clouds. This is most probably because they can be easily seen from the ground at latitudes above about 55 degrees and in addition numerous papers have reported quantitative cloud properties from space borne measurements. In recent years the focus on PMCs has intensified as a result of satellite measurements that show increasing cloud brightness and frequency of occurrence over the last ~ 27 years. Also, while not conclusively shown, it seems that there are more frequent cloud sightings at lower latitudes, e.g. 40 N, than have been reported in the past. Finally, there is the unproven but plausible theory that the observed changes in cloud properties are connected with global change due to the buildup of the greenhouse gases, CO2 and CH4, in the atmosphere.
This paper will present an overview of space-based observations of PMCs and scientific implications of the data. The clouds have been extensively observed by a number of satellite experiments. AIM is the first mission dedicated to the study of PMCs with the overall goal being to understand why they form and vary. PMC temporal variability on time scales of a solar cycle and the 27-day solar rotation have been reported. We also now know that PMCs are highly variable from orbit-to-orbit and day-to-day with significant complex structure. Other analyses show that temperature change is a dominant factor in controlling season onset, variability during the season and season end. Rising water vapor levels at the beginning and falling values at the end also play a key role in season initiation and cessation. Structures seen in the clouds look very much like complex features seen in tropospheric clouds including large regions of near circular ice voids. Planetary waves modulate PMC occurrence and can effectively extend the PMC season by providing several days of localized regions of saturated air in the troughs of the waves. By contrast, gravity waves appear to locally diminish PMC frequency even though global scale gravity wave drag is acknowledged as the prime cause of the cold polar summer mesopause. Satellite results also provide evidence that interhemispheric coupling, from the winter hemisphere to the summer hemisphere affects PMC variability.
18:00 - 18:20 - Effects of cosmic rays on clouds and snow-fall in Antarctica (C. P. Anil Kumar)