Flight Planning: Near Real-time Assimilation

Investigation Description: We will produce assimilated winds and temperatures using the GEOS-2 Data Assimilation System (DAS) in near real-time for the duration of the SOLVE mission. Assimilated forecasts will be used in flight planning and the assimilated analyses will be used in post-flight data analyses. We will also use forecast winds to run a mountain wave forecast model, relevant to the goals of pilot safety and to flying Lagrangian flight tracks. Our assimilated products will be also used as meteorological input by three other SOLVE theory investigations for production of additional flight planning and data analysis products.

Forecasts of mountain wave vertical displacement amplitudes, temperature amplitudes and turbulence production will be provided at reference pressure levels in the troposphere and stratosphere during SOLVE, using the Naval Research Laboratory Mountain Wave Forecast Model (MWFM) interfaced to DAO forecast winds and temperatures over the Scandinavia region. Further information can also be found at the MWFM home page.

Recent Meteorological Support for ER-2 Campaigns: The GEOS-DAS has been the primary tool for forecasting and flight planning for four recent ER-2 campaigns: SPADE, ASHOE/MAESA, STRAT, and POLARIS. As a flight planning tool, it is used predict the location of features such as the vortex edge, vortex filaments, and low temperature regions which may form PSCs. As an analysis tool, the analyzed meteorological fields provide the dynamical framework necessary for the interpretation of aircraft measurements. The GEOS-DAS forecast winds have also played an important role in previous missions by providing meteorological input for the Naval Research Laboratory Mountain Wave Forecast Model (NRL/MWFM). This model, which was developed at NASA Goddard more than six years ago, has been used to forecast stratospheric mountain wave activity for every ER-2 campaign since AASE-II. Mountain wave forecasts are an essential flight-planning tool because they help ER-2 pilots avoid hazardous mountain wave-induced turbulence.

Contribution to the SOLVE Campaign: We will produce near real-time stratospheric meteorological forecasts and analyses in support of flight and mission planning for the duration of the SOLVE mission. We will send an assimilation production person into the field for the first 1-2 weeks of each DC-8 and ER-2 deployment to make certain the assimilated products are customized to the mission scientists needs and available in a timely manner. We will also provide forecasts and analyses of mountain wave activity during the ER-2 deployment using the NRL/MWFM with GEOS-DAS winds. These forecasts will aid safe flight planning. This is very important for SOLVE ER-2 flights, which will involve high-altitude flights over significant topography (e.g., Greenland, the Scandinavian ridge, and Iceland) in the remote polar environment. These forecasts will also help in planning possible ER-2 encounters with large amplitude (nonturbulent) mountain waves which produce polar stratospheric ice clouds and associated ozone depletion in the Arctic winter stratosphere [Carslaw et al., 1998a].

Assimilated products are essential for three other SOLVE investigations. The Lait et al. investigation (Meteorological Forecasting) will use the assimilated forecasts to calculate back trajectories along the proposed flight tracks to assist in flight planning. The investigation of Kawa et al. (Three-dimensional and trajectory chemistry and transport modeling) will do near real-time chemistry forecasting using the Goddard CTM in the same manner as in POLARIS. The investigation of Pierce et al. ("HALOE/SAGE III Lagrangian forecasting") will use both forecast and analyzed winds to calculate Lagrangian chemical trajectories. Near real-time assimilated products will be available approximately 1 November 1999 for users of the products to begin testing and fine-tuning their software.

Relevance to SOLVE Objectives: The primary science objective of SOLVE is to further understand processes controlling polar stratospheric ozone. The near real-time assimilation responds to that objective by making possible a suite of forecast products that allow mission scientists to optimize the science return of every flight. The GEOS-DAS forecasts of winds and temperature allow mission scientists to examine meteorological conditions within the aircraft’ flight range in order to identify possible flight tracks for the desired measurements. When the forecast winds are used as input to the Goddard trajectory model (the Lait et al. investigation), temperature and solar exposure histories of the air parcels along the proposed flight track can also be determined. This provides input for mission scientists that helps optimize the flight track. The Kawa et al. investigation uses the forecast winds to produce chemical forecasts of radical and reservoir species, providing further information to maximize science return from the proposed flight track. Later, analyzed assimilated winds will be used to run the full chemistry CTM to calculate both the chemical and dynamical contributions to dO₃/dt from late fall through the end of winter. The Mountain Wave Forecast Model not only provides information relevant to pilot safety along proposed flight tracks, its forecasts also show the behavior of mountain- forced waves and identify possible Lagrangian flight tracks, a stated goal of SOLVE.

According to the SOLVE NRA, Lagrangian flights will be needed over Iceland, Scandinavia, and Russia. These flight tracks will be used to measure chlorine deactivation (ClO --> ClONO₂) and denitrification, and thereby assess our understanding of this photochemistry. Carslaw et al. [1998b] have shown that mountain waves produced by flow over the Scandinavian ridge during January, 1995, produced stratospheric ice clouds. Due to heterogeneous chemistry within these clouds, this led to appreciable levels of ozone depletion downwind of these wave clouds. Using representative NRL/MWFM predictions of Arctic mountain wave activity, they argued that similar wave cloud-induced ozone depletion elsewhere in the Arctic could produce an overall decrease in ozone in the winter Arctic stratosphere. For the SOLVE mission, NRL/MWFM forecasts will allow possible large-amplitude nonturbulent mountain waves with associated ice clouds to be identified for possible encounters with the ER-2. This would be especially valuable, since only limited remote sensing of these Arctic wave clouds has occurred to date, leaving many questions regarding their nonequilibrium microphysics and heterogeneous chemistry unanswered.