AIM CIPS PMC tracking wind product retrieval approach and first assessment

Case study of an ice void structure in polar mesospheric clouds

Retrieval of polar mesospheric cloud properties from CIPS: Algorithm description, error analysis and cloud detection sensitivity

The cloud imaging and particle size (CIPS) instrument onboard the Aeronomy of Ice in the Mesosphere satellite provides images of gravity waves (GWs) near the stratopause and lowermost mesosphere (altitudes of 50–55 km). GW identification is based on Rayleigh Albedo Anomaly (RAA) variances, which are derived from GW‐induced fluctuations in Rayleigh scattering at 265 nm. Based on 3 years of CIPS RAA variance data from 2019 to 2022, we report for the first time the seasonal distribution of GWs entering the mesosphere with high (7.5 km) horizontal resolution on a near‐global scale. Seasonally averaged GW variances clearly show spatial and temporal patterns of GW activity, mainly due to the seasonal variation of primary GW sources such as convection, the polar vortices and flow over mountains. Measurements of stratospheric GWs derived from Atmospheric InfraRed Sounder (AIRS) observations of 4.3 μm brightness temperature perturbations within the same 3‐year time range are compared to the CIPS results. The comparisons show that locations of GW hotspots are similar in the CIPS and AIRS observations. Variability in GW variances and the monthly changes in background zonal wind suggest a strong GW‐wind correlation. This study demonstrates the utility of the CIPS GW variance data set for statistical investigations of GWs in the lowermost mesosphere, as well as provides a reference for location/time selection for GW case studies.

This study describes atmospheric forcing parameters constructed from different global climatologies, applied to the Black Sea, and investigates the sensitivity of Hybrid Coordinate Ocean Model (HYCOM) simulations to these products. Significant discussion is devoted to construction of these parameters before using them in the eddy-resolving (≈3.2-km resolution) HYCOM simulations. The main goal is to answer how the model dynamics can be substantially affected by different atmospheric forcing products in the Black Sea. Eight wind forcing products are used: four obtained from observation-based climatologies, including one based on measurements from the SeaWinds scatterometer on the Quick Scatterometer (QuikSCAT) satellite, and the rest formed from operational model products. Thermal forcing parameters, including solar radiation, are formed from two operational models: the European Centre for Medium-Range Weather Forecasts (ECMWF) and the Fleet Numerical Meteorology and Oceanography Center (FNMOC) Navy Operational Global Atmospheric Prediction System (NOGAPS). Climatologically forced Black Sea HYCOM simulations (without ocean data assimilation) are then performed to assess the accuracy and sensitivity of the model sea surface temperature (SST) and sea surface circulation to these wind and thermal forcing products. Results demonstrate that the model-simulated SST structure is quite sensitive to the wind and thermal forcing products, especially near coastal regions. Despite this sensitivity, several robust features are found in the model SST in comparison to a monthly 9.3-km-resolution satellite-based Pathfinder SST climatology. Annual mean HYCOM SST usually agreed to within ≈±0.2° of the climatology in the interior of the Black Sea for any of the wind and thermal forcing products used. The fine-resolution (0.25° × 0.25°) wind forcing from the scatterometer data along with thermal forcing from NOGAPS gave the best SST simulation with a basin-averaged rms difference value of 1.21°C, especially improving model results near coastal regions. Specifically, atmospherically forced model simulations with no assimilation of any ocean data suggest that the basin-averaged rms SST differences with respect to the Pathfinder SST climatology can vary from 1.21° to 2.15°C depending on the wind and thermal forcing product. The latter rms SST difference value is obtained when using wind forcing from the National Centers for Environmental Prediction (NCEP), a product that has a too-coarse grid resolution of 1.875° × 1.875° for a small ocean basin such as the Black Sea. This paper also highlights the importance of using high-frequency (hybrid) wind forcing as opposed to monthly mean wind forcing in the model simulations. Finally, there are large variations in the annual mean surface circulation simulated using the different wind sets, with general agreement between those forced by the model-based products (vector correlation is usually >0.7). Three of the observation-based climatologies generally yield unrealistic circulation features and currents that are too weak.

We explore the effects of lower thermospheric water vapor deposited by launch vehicle plumes on polar mesospheric cloud (PMC) frequencies at 80°N. We use July‐averaged PMC frequencies from 2007 to 2022 from the Cloud Imaging and Particle Size (CIPS) instrument on NASA's Aeronomy of Ice in the Mesosphere (AIM) satellite. Launch sites worldwide are typically located near northern mid‐latitudes. Using the orbital launch record for the same time period, we find that the number of launches correlates with PMC frequencies with a coefficient of r = 0.60, which increases to r = 0.75 when only selecting launches from 2.5 to 21.5 local time (LT), indicating a weak LT dependence on global‐scale transport to 80°N. To support our findings, we use meridional winds from the Michelson Interferometer for Global High‐resolution Imaging experiment on NASA's Ionospheric Connection Explorer satellite and winds from the Horizontal Wind Model climatology to interpret the northward motion of air parcels at 105 km. We find the launch LT window that maximizes the correlation coefficient to be consistent with the expected maximum northward motion from the diurnal variation of mid‐latitude meridional winds. Comparisons with Microwave Limb Sounder satellite observations of upper mesospheric temperature and water vapor reveal a strong dependence of cloud frequency on water vapor (r = 0.86) but not on temperature (r = −0.26), indicating that water vapor is the primary source of PMC variability for the bright PMCs at 80°N. We therefore find that launch vehicle plumes originating primarily from northern mid‐latitudes modulate PMC frequency at 80°N in July.

We examine the evolution of the quasi 2‐day wave in the middle atmosphere during the period from 5 January to 5 February 2006 using global synoptic meteorological fields from the high‐altitude Navy Operational Global Atmospheric Prediction System Advanced Level Physics, High Altitude (NOGAPS‐ALPHA) forecast‐assimilation system. This period is characterized by a high level of planetary wave activity in the Northern Hemisphere (winter) extratropical stratosphere prior to a sudden stratospheric warming (SSW) on 20 January 2006. Space‐time spectral analysis of 6‐hourly NOGAPS‐ALPHA fields finds the largest quasi 2‐day wave amplitudes in the Southern Hemisphere (summer) extratropical upper mesosphere. Eliassen‐Palm flux diagnostics indicate that this extratropical quasi 2‐day wave is related to baroclinic instability along the equatorward flank of the summer easterly jet. The quasi 2‐day wave is also evident in NOGAPS‐ALPHA water vapor fields near the tropical stratopause and is related to barotropic instability. We find that the strong planetary wave activity leading up to the SSW produced an enhanced northward component of the residual meridional circulation that influenced the background zonal winds and, by extension, the quasi 2‐day wave forcing in both the tropical and extratropical regions. In the tropical region, the combination of enhanced horizontal momentum advection by the residual meridional circulation and inertially unstable circulations related to planetary wave breaking in the subtropics produced conditions favoring barotropic instability. In the extratropical region, the enhanced residual meridional circulation altered the zonal wind tendency through increased Coriolis torque.

Recent advances in data processing from the Cloud Imaging and Particle Size (CIPS) instrument on the NASA Aeronomy of Ice in the Mesosphere satellite allow observation of bright mesospheric clouds at mid‐latitudes (<60°). When adjusted for the evolving local time (LT) of the CIPS observations during its mission we find that the frequencies of these bright clouds in the northern hemisphere show no trend from 2007 to 2021 and no dependence on the solar cycle, although the interannual variability is extreme. Rather we investigate the possible link with propellant exhaust from orbital vehicles, typically launched at lower latitudes. By filtering the launch record equatorward of 60°N using only those launches between 23 and 10 LT, we find a strong correlation with the observed mid‐latitude mesospheric cloud frequency variability between 56° and 60°N. Meridional winds at 92 km from a meteorological analysis system reveal that these morning launches occurred at the time of maximum northward transport. Based upon this combination of high correlation between the cloud frequency and the launch record plus favorable transport conditions, it is likely that space traffic has a strong influence on the interannual variability of these bright mesospheric clouds.

A high-altitude version of the Navy Operational Global Atmospheric Prediction System (NOGAPS) spectral forecast model is used to simulate the unusual September 2002 Southern Hemisphere stratospheric major warming. Designated as NOGAPS-Advanced Level Physics and High Altitude (NOGAPS-ALPHA), this model extends from the surface to 0.005 hPa (∼85 km altitude) and includes modifications to multiple components of the operational NOGAPS system, including a new radiative heating scheme, middle-atmosphere gravity wave drag parameterizations, hybrid vertical coordinate, upper-level meteorological initialization, and radiatively active prognostic ozone with parameterized photochemistry. NOGAPS-ALPHA forecasts (hindcasts) out to 6 days capture the main features of the major warming, such as the zonal mean wind reversal, planetary-scale wave amplification, large upward Eliassen–Palm (EP) fluxes, and splitting of the polar vortex in the middle stratosphere. Forecasts beyond 6 days have reduced upward EP flux in the lower stratosphere, reduced amplitude of zonal wavenumbers 2 and 3, and a middle stratospheric vortex that does not split. Three-dimensional EP-flux diagnostics in the troposphere reveal that the longer forecasts underestimate upward-propagating planetary wave energy emanating from a significant blocking pattern over the South Atlantic that played a large role in forcing the major warming. Forecasts of less than 6 days are initialized with the blocking in place, and therefore are not required to predict the blocking onset. For a more thorough skill assessment, NOGAPS-ALPHA forecasts over 3 weeks during September–October 2002 are compared with operational NOGAPS 5-day forecasts made at the time. NOGAPS-ALPHA forecasts initialized with 2002 operational NOGAPS analyses show a modest improvement in skill over the NOGAPS operational forecasts. An additional, larger improvement is obtained when NOGAPS-ALPHA is initialized with reanalyzed 2002 fields produced with the currently operational (as of October 2003) Naval Research Laboratory (NRL) Atmospheric Variational Data Assimilation System (NAVDAS). Thus the combination of higher model top, better physical parameterizations, and better initial conditions all yield improved forecasting skill over the NOGAPS forecasts issued operationally at the time.

The evolution of the upper ocean in the strong seasonally forced Arabian Sea, as observed by a mooring deployed in 1994–1995, is investigated using the Naval Research Laboratory Layered Ocean Model (NLOM). Model simulations were sensitive to the choice of surface wind products used for forcing, and results are reported for simulations forced by monthly mean climatologies and 12 hourly 1994–1995 wind products from two operational atmospheric forecast models, the European Centre for Medium‐Range Weather Forecast model and the Navy Operational Global Atmospheric Prediction System model of Fleet Numerical Meteorology and Oceanography Center (FNMOC). The NLOM yields the best prediction of sea surface temperature (SST) and mixed layer depth when using FNMOC forcing. Surface cooling is found to be responsible for the seasonal SST minimum during the NE monsoon. Heat advection is found to be important for supporting the surface cooling during the second half of the NE monsoon. Strong entrainment and appreciable advective cooling are responsible for the SST minimum of the SW monsoon. The NLOM wind experiments strongly suggest that thermal convection may be important in the central Arabian Sea during the winter months.

At the Fleet Numerical Oceanography Center, two computer models, the Navy Operational Global Atmospheric Prediction System, NOGAPS, and the Navy Operational Regional Atmospheric Prediction System, NORAPS, generate a twice-daily suite of atmospheric analyses and forecasts. NOGAPS is the driving force behind many of the center's products and has become a complex, highly structured system designed to run automatically. The execution of NOGAPS and NORAPS within the operational schedule is described. The systems consist of 1) automated data processing and quality control, 2) a multivariate optimum interpolation analysis, 3) initialization and forecast, and 4) output. The data-processing step is shared between the two systems.

Based on long-term observations from Wuhan and Beijing MST (Mesosphere-Stratosphere-Troposphere) radars, we analyzed the climatological properties of mid-latitude mesospheric winds and evaluated them against the Horizontal Wind Model (HWM14). Measurements of zonal and meridional winds were collected from 2012 to 2021 using these two MST radars. The seasonal daily and monthly variations and periodic oscillations in mesospheric zonal and meridional winds are presented. Monthly mean and seasonal zonal winds recorded by two MST radars have similar height-time distributions to the HWM14. However, there are differences in zonal wind speeds, especially between summer and winter measurements and HWM14. The agreement between model results and actual radar measurements is poorer for meridional winds than for zonal winds. Through harmonic analysis, it is revealed that the zonal and meridional winds display significant Annual Oscillation (AO) between 65 and 85 km, while Semi-Annual Oscillation (SAO) is not readily apparent. It is found that there is no significant correlation between solar activity and the wind variations or data acquisition rate from MST radar. Overall, these studies help us better understand atmospheric changes in the mesosphere and provide ground observation references for models.

The convective parameterization of Emanuel has been employed in the forecast model of the Navy Operational Global Atmospheric Prediction System (NOGAPS) since 2000, when it replaced a version of the relaxed Arakawa–Schubert scheme. Although in long-period data assimilation forecast tests the Emanuel scheme has been found to perform quite well in NOGAPS, particularly for tropical cyclones, some weaknesses have also become apparent. These weaknesses include underprediction of heavy-precipitation events, too much light precipitation, and unrealistic heating at upper levels. Recent research efforts have resulted in modifications of the scheme that are designed to reduce such problems. One change described here involves the partitioning of the cloud-base mass flux into mixing cloud mass flux at individual levels. The new treatment significantly reduces a heating anomaly near the tropopause that is associated with a large amount of mixing cloud mass flux ascribed to that region in the original Emanuel ...

Seventy-two-hour forecasts of sea level cyclones from the Navy Operational Global Atmospheric Prediction System are examined. Cyclones that formed over the North Pacific region of maximum cyclogenesis frequency are included for study. The analysis is oriented to assist the forecaster in evaluating the numerical model guidance by emphasizing verification of operationally oriented factors (i.e., cyclogenesis, explosive deepening). Initially, systematic errors in forecast intensities and positions are identified. Maximum underforecasting errors (forecast central pressure higher than actual central pressure) occur over the central North Pacific region of climatological maximum cyclone deepening. Maximum overforecasting errors (forecast central pressure lower than the actual central pressure) occur over the region of climatological cyclone dissipation. Maximum position errors also occur over the central North Pacific region of climatological maximum deepening. These systematic error distributions indi...

A high-order accurate radiative transfer (RT) model developed by Fu and Liou has been implemented into the Navy Operational Global Atmospheric Prediction System (NOGAPS) to improve the energy budget and forecast skill. The Fu–Liou RT model is a four-stream algorithm (with a two-stream option) integrating over 6 shortwave bands and 12 longwave bands. The experimental 10-day forecasts and analyses from data assimilation cycles are compared with the operational output, which uses a two-stream RT model of three shortwave and five longwave bands, for both winter and summer periods. The verifications against observations of radiosonde and surface data show that the new RT model increases temperature accuracy in both forecasts and analyses by reducing mean bias and root-mean-square errors globally. In addition, the forecast errors also grow more slowly in time than those of the operational NOGAPS because of accumulated effects of more accurate cloud–radiation interactions. The impact of parameterized cloud effective radius in estimating liquid and ice water optical properties is also investigated through a sensitivity test by comparing with the cases using constant cloud effective radius to examine the temperature changes in response to cloud scattering and absorption. The parameterization approach is demonstrated to outperform that of constant radius by showing smaller errors and better matches to observations. This suggests the superiority of the new RT model relative to its operational counterpart, which does not use cloud effective radius. An effort has also been made to improve the computational efficiency of the new RT model for operational applications.

The Navy Operational Global Atmospheric Prediction System (NOGAPS) has proven itself to be competitive with any of the large forecast models run by the large operational forecast centers around the world. The navy depends on NOGAPS for an astonishingly wide range of applications, from ballistic winds in the stratosphere to air-sea fluxes to drive ocean general circulation models. Users of these applications will benefit from a better understanding of how a system such as NOGAPS is developed, what physical assumptions and compromises have been made, and what they can reasonably expect in the future as the system continues to evolve. The discussions will be equally relevant for users of products from other large forecast centers, e.g., National Meteorological Center, European Centre for Medium-Range Weather Forecasts. There is little difference in the scientific basis of the models and the development methodologies used for their development. However, the operational priorities of each center and t...