Middle and Lower Atmosphere Michael Kelley Topics - Vertical Coupling by Waves Tidal Characterization and Variability Instabilities Global Coverage Instrumental Requirements and Campaigns Middle and Lower Atmosphere

Gravity Wave Coupling critical level Gravity Wave (GW) Sources: GW excitation mechanisms. Climatology of GW source distribution. Spectral components of various wave sources. ==> Physics-consistent specifications of GW in GCM. GW propogation and breaking Quantify subgrid processes related to wave breaking. Multiscale interactions: Two way interactions with mean circulation, planetary waves, and tides. Implications of GW geographical and temporal variability. critical level Alexander and Holton (2000) Middle and Lower Atmosphere

Middle and Lower Atmosphere Tidal Variability Gravity Wave Interactions : Planetary Wave Interactions Middle and Lower Atmosphere

Middle and Lower Atmosphere Tides Annual, daily, and subdaily atmospheric tides are seen in surface pressure, GPS-derived tropospheric delay, and mesospheric winds Atmospheric tides dominate the dynamics of the mesosphere-lower thermosphere (MLT). Middle and Lower Atmosphere

Middle and Lower Atmosphere Wind Models Climatology The de facto neutral wind model in current use is HWM-93 In the MLT, data sources were MF radar, meteor radar, incoherent scatter radar, rocketsondes, rocket grenade sounding, and gradient winds No direct Doppler wind measurements measured either by ground based or satellite based platforms were ever included in the Horizontal Wind Model for MLT winds Presently, 15 years of HRDI, WINDII, and TIDI wind measurements plus a significant ground based database are ignored in HWM climatology Space Weather Significant differences exist in MLT winds as a function of longitude Propose studies that advance: Understanding long term MLT climatology Better appreciation of longitudinal tidal differences Middle and Lower Atmosphere

Middle and Lower Atmosphere Why predict or assimilate the Mesosphere and Lower Thermosphere? Couple the neutral atmosphere to high altitude “space weather” disturbances. Couple MLT to troposphere: knowledge of gravity wave sources and intermittency factors are critical for GW parameterizations in MLT. MLT low density and low thermal “inertia” make this region very sensitive to “change” (climate or otherwise), compared to troposphere. Models estimates suggest a decline in MLT temperature associated with increases in CO2 and N2O concentrations. Models have addressed only the thermodynamic and radiative transfer aspects of the problem for a global mean. Long-term dynamic changes strongly affect the filtering of gravity waves, offering a continuing challenge for modelling efforts. Long-term observations are ambiguous regarding the direction of changes. Identification of the sources of variations on all time scales will help sort out the relative contribution of these sources to long-term change. Middle and Lower Atmosphere

Middle and Lower Atmosphere

Middle and Lower Atmosphere

Middle and Lower Atmosphere NLC over Finland courtesy P. Parviainen Ice Clouds in the Mesosphere and their Variability Noctilucent clouds (NLC) were discovered over 100 years ago They are the Earth’s highest clouds (~82 km) and comprise microscopic ice crystals (~50nm radius) that form and grow in the vicinity of the high-latitude cold summer mesopause (T < 130 K). Satellite measurements have established the existence of extensive clouds in the Arctic and Antarctic summer polar mesosphere (called PMC) Models of PMC formation show that super-saturated regions must be present for cloud nucleation. Yet, there are still no comprehensive knowledge of the chemical/thermal environment in which PMC form. SNOE PMC data Middle and Lower Atmosphere

Middle and Lower Atmosphere Instabilities Convective Instability (R.T.) Thermal structure influenced by mean state (winter/summer), D&SD Tides, PW, and AGWs. Shear Instability (K.H.) Strong tides and tide/AGW coupling contribute Effects Overturning (heat and constituent transport), MILs, Ripples, Stress Middle and Lower Atmosphere

Middle and Lower Atmosphere Instruments with higher temporal and spatial resolutions Lidars (T, winds) , imagers (airglow, ripples, temperture), radar (winds) Simulations, models, waves, NEW (Extend to lower altitudes and expanded information withing the MLT) Tomography with multi-view, multispectral (airglow layer) image inversion Lidar, Rayleigh with power (50-80 km) Aircraft, rocket, and balloon correlative campaigns Middle and Lower Atmosphere

Middle and Lower Atmosphere Proposed AMISR/AkFPI ion-neutral coupling campaign All-sky imagers would document particle preciptiation distribution Green-shaded regions cover range of zenith angles from: 20° minimum to 45° maximum Five common volume points would be observed in sequence so that 5 neutral wind vectors are fully determined. These points, CV 1- CV 5, would be sequentially surveyed by the 3 FPI instruments in synchronized mode. The AMISR would provide similar coverage re the 5 CV points. Vorticity would be calculated for each of the four triangles shown. Variations would be particularly interesting during substorm activity. The CV points would be supplemented by additional points in the zenith, zonal and meridional directions for each FPI observatory. • 20 45 Middle and Lower Atmosphere

Middle and Lower Atmosphere Prospects for the usefulness of tropospheric delay data (cont'd): Sensitivity of GPS-derived ZTD appears to be sufficient to resolve subdaily oscillations including the lunar (gravitational) tidal oscillation at L2. Sidebands here reflect annual modulation of the S2 tide. Enhanced power around S2 indicates modulation of the S2 tide by planetary waves. A global network of dual-frequency GPS receivers allows one to analyze tropospheric tidal phenomena by wave decomposition. Network density will increase with the availability of low-cost dual-frequency receivers. Precise point positioning (PPP) allows ZTD to be calculated for any dual-frequency GPS receiver. Future developments offer promise: ZTD estimation strategy continues to be refined. A second civilian GPS signal (~2010) will allow for accurate and inexpensive dual-frequency GPS receivers. The advent of the European GPS system (Galileo) will increase accuracy and density of measurements. Middle and Lower Atmosphere

Middle and Lower Atmosphere Proposed Class I Instruments and Coordinated Campaigns Beef up all 3 sodium lidars in the CRRL to 24-hour capability and large telescope Mobile lidars in concert with AMISR More stations (both radar and lidar) to cover minimal longitudes and latitudes as required by modelers Community designed (led by modelers and wave specialists, reality-checked by instrument “owners”) coordinated campaigns.. Middle and Lower Atmosphere