scholarly journals Accuracy of Balloon Trajectory Forecasts in the Lower Stratosphere

Atmosphere ◽  
2019 ◽  
Vol 10 (2) ◽  
pp. 102 ◽  
Author(s):  
Selvaraj Dharmalingam ◽  
Riwal Plougonven ◽  
Albert Hertzog ◽  
Aurélien Podglajen ◽  
Michael Rennie ◽  
...  
Keyword(s):  
Lower Stratosphere ◽  
Weather Prediction ◽  
Large Error ◽  
Vertical Resolution ◽  
Operational Strategies ◽  
Weather Forecasts ◽  
Long Duration ◽  
Median Error ◽  
Prediction Systems ◽  
The Impact

This paper investigates the accuracy of simulated long-duration super-pressure balloon trajectories in the lower stratosphere. The observed trajectories were made during the (tropical) Pre-Concordiasi and (polar) Concordiasi campaigns in 2010, while the simulated trajectories are computed using analyses and forecasts from the European Centre for Medium-Range Weather Forecasts (ECMWF) Integrated Forecast System model. In contrast with the polar stratosphere situation, modelling accurate winds in the tropical lower stratosphere remains challenging for numerical weather prediction systems. The accuracy of the simulated tropical trajectories are quantified with the operational products of 2010 and 2016 in order to understand the impact of model physics and vertical resolution improvements. The median errors in these trajectories are large (typically ≳ 250 km after 24 h), with a significant negative bias in longitude, for both model versions. In contrast, using analyses in which the balloon-borne winds have been assimilated reduces the median error in the balloon position after 24 h to ∼60 km. For future campaigns, we describe operational strategies that take advantage of the geographic distribution and the episodic nature of large error events to anticipate the amplitude of error in trajectory forecasts. We finally stress the importance of a high vertical resolution in the model, given the intense shears encountered in the tropical lower stratosphere.

scholarly journals Issues Regarding the Assimilation of Cloud and Precipitation Data

2007 ◽  
Vol 64 (11) ◽  
pp. 3785-3798 ◽  
Author(s):  
Ronald M. Errico ◽  
Peter Bauer ◽  
Jean-François Mahfouf
Keyword(s):  
Weather Prediction ◽  
Difficult Problem ◽  
Careful Examination ◽  
Weather Forecasts ◽  
Clear Sky ◽  
Precipitation Characteristics ◽  
Satellite Radiance Data ◽  
Prediction Systems ◽  
Radiance Data ◽  
Peculiar Nature

Abstract The assimilation of observations indicative of quantitative cloud and precipitation characteristics is desirable for improving weather forecasts. For many fundamental reasons, it is a more difficult problem than the assimilation of conventional or clear-sky satellite radiance data. These reasons include concerns regarding nonlinearity of the required observation operators (forward models), nonnormality and large variances of representativeness, retrieval, or observation–operator errors, validation using new measures, dynamic and thermodynamic balances, and possibly limited predictability. Some operational weather prediction systems already assimilate precipitation observations, but much more research and development remains. The apparently critical, fundamental, and peculiar nature of many issues regarding cloud and precipitation assimilation implies that their more careful examination will be required for accelerating progress.

scholarly journals Added-value of GEO-hyperspectral Infrared Radiances for Local Severe Storm Forecasts Using the Hybrid OSSE Method

2021 ◽  
Author(s):  
Pei Wang ◽  
Zhenglong Li ◽  
Jun Li ◽  
Timothy J. Schmit
Keyword(s):  
Spectral Resolution ◽  
Weather Prediction ◽  
Atmospheric Temperature ◽  
Added Value ◽  
High Spectral Resolution ◽  
Vertical Resolution ◽  
Severe Storm ◽  
Impact Studies ◽  
High Vertical Resolution ◽  
The Impact

AbstractHigh spectral resolution (or hyperspectral) infrared (IR) sounders onboard low earth orbiting satellites provide high vertical resolution atmospheric information for numerical weather prediction (NWP) models. In contrast, imagers on geostationary (GEO) satellites provide high temporal and spatial resolution which are important for monitoring the moisture associated with severe weather systems, such as rapidly developing local severe storms (LSS). A hyperspectral IR sounder onboard a geostationary satellite would provide four-dimensional atmospheric temperature, moisture, and wind profiles that have both high vertical resolution and high temporal/spatial resolutions. In this work, the added-value from a GEO-hyperspectral IR sounder is studied and discussed using a hybrid Observing System Simulation Experiment (OSSE) method. A hybrid OSSE is distinctively different from the traditional OSSE in that, (a) only future sensors are simulated from the nature run and (b) the forecasts can be evaluated using real observations. This avoids simulating the complicated observation characteristics of the current systems (but not the new proposed system) and allows the impact to be assessed against real observations. The Cross-track Infrared Sounder (CrIS) full spectral resolution (FSR) is assumed to be onboard a GEO for the impact studies, and the GEO CrIS radiances are simulated from the ECMWF Reanalysis v5 (ERA5) with the hyperspectral IR all-sky radiative transfer model (HIRTM). The simulated GEO CrIS radiances are validated and the hybrid OSSE system is verified before the impact assessment. Two LSS cases from 2018 and 2019 are selected to evaluate the value-added impacts from the GEO CrIS-FSR data. The impact studies show improved atmospheric temperature, moisture, and precipitation forecasts, along with some improvements in the wind forecasts. An added-value, consisting of an overall 5% Root Mean Square Error (RMSE) reduction, was found when a GEO CrIS-FSR is used in replacement of LEO ones indicating the potential for applications of data from a GEO hyperspectral IR sounder to improve local severe storm forecasts.

scholarly journals Assessment of Radio Occultation Observations from the COSMIC-2 Mission with a Simplified Observing System Simulation Experiment Configuration

2017 ◽  
Vol 145 (9) ◽  
pp. 3581-3597 ◽  
Author(s):  
L. Cucurull ◽  
R. Li ◽  
T. R. Peevey
Keyword(s):  
Radio Occultation ◽  
Weather Forecasting ◽  
System Simulation ◽  
Weather Prediction ◽  
Forecast Model ◽  
Forecast Skill ◽  
Weather Forecasts ◽  
Global Coverage ◽  
Prediction Systems ◽  
Observing System Simulation Experiment

The mainstay of the global radio occultation (RO) system, the COSMIC constellation of six satellites launched in April 2006, is already past the end of its nominal lifetime and the number of soundings is rapidly declining because the constellation is degrading. For about the last decade, COSMIC profiles have been collected and their retrievals assimilated in numerical weather prediction systems to improve operational weather forecasts. The success of RO in increasing forecast skill and COSMIC’s aging constellation have motivated planning for the COSMIC-2 mission, a 12-satellite constellation to be deployed in two launches. The first six satellites (COSMIC-2A) are expected to be deployed in December 2017 in a low-inclination orbit for dense equatorial coverage, while the second six (COSMIC-2B) are expected to be launched later in a high-inclination orbit for global coverage. To evaluate the potential benefits from COSMIC-2, an earlier version of the NCEP’s operational forecast model and data assimilation system is used to conduct a series of observing system simulation experiments with simulated soundings from the COSMIC-2 mission. In agreement with earlier studies using real RO observations, the benefits from assimilating COSMIC-2 observations are found to be most significant in the Southern Hemisphere. No or very little gain in forecast skill is found by adding COSMIC-2A to COSMIC-2B, making the launch of COSMIC-2B more important for terrestrial global weather forecasting than that of COSMIC-2A. Furthermore, results suggest that further improvement in forecast skill might better be obtained with the addition of more RO observations with global coverage and other types of observations.

scholarly journals A Similarity-Based Implementation of the Schaake Shuffle

2016 ◽  
Vol 144 (5) ◽  
pp. 1909-1921 ◽  
Author(s):  
Roman Schefzik
Keyword(s):  
Prediction Models ◽  
Initial Conditions ◽  
Weather Prediction ◽  
Similarity Criterion ◽  
Ensemble Prediction ◽  
Ensemble Forecasts ◽  
Weather Forecasts ◽  
Prediction Horizon ◽  
Prediction Systems ◽  
Specific Implementation

Contemporary weather forecasts are typically based on ensemble prediction systems, which consist of multiple runs of numerical weather prediction models that vary with respect to the initial conditions and/or the parameterization of the atmosphere. Ensemble forecasts are frequently biased and show dispersion errors and thus need to be statistically postprocessed. However, current postprocessing approaches are often univariate and apply to a single weather quantity at a single location and for a single prediction horizon only, thereby failing to account for potentially crucial dependence structures. Nonparametric multivariate postprocessing methods based on empirical copulas, such as ensemble copula coupling or the Schaake shuffle, can address this shortcoming. A specific implementation of the Schaake shuffle, called the SimSchaake approach, is introduced. The SimSchaake method aggregates univariately postprocessed ensemble forecasts using dependence patterns from past observations. Specifically, the observations are taken from historical dates at which the ensemble forecasts resembled the current ensemble prediction with respect to a specific similarity criterion. The SimSchaake ensemble outperforms all reference ensembles in an application to ensemble forecasts for 2-m temperature from the European Centre for Medium-Range Weather Forecasts.

scholarly journals SINGV – the Convective-Scale Numerical Weather Prediction System for Singapore

2019 ◽  
Vol 36 (3) ◽  
Author(s):  
Xiang-Yu Huang ◽  
Dale Barker ◽  
Stuart Webster ◽  
Anurag Dipankar ◽  
Adrian Lock ◽  
...  
Keyword(s):  
Numerical Weather Prediction ◽  
Weather Prediction ◽  
Extreme Rainfall ◽  
Prediction System ◽  
Local Data ◽  
Weather Forecasts ◽  
Numerical Weather ◽  
The United Kingdom ◽  
Convective Scale ◽  
The Impact

Extreme rainfall is one of the primary meteorological hazards in Singapore, as well as elsewhere in the deep tropics, and it can lead to significant local flooding. Since 2013, the Meteorological Service Singapore (MSS) and the United Kingdom Met Office (UKMO) have been collaborating to develop a convective-scale Numerical Weather Prediction (NWP) system, called SINGV. Its primary aim is to provide improved weather forecasts for Singapore and the surrounding region, with a focus on improved short-range prediction of localized heavy rainfall. This paper provides an overview of the SINGV development, the latest NWP capabilities at MSS and some key results of evaluation. The paper describes science advances relevant to the development of any km-scale NWP suitable for the deep tropics and provides some insights into the impact of local data assimilation and utility of ensemble predictions.

scholarly journals Relative importance of tropopause structure and diabatic heating for baroclinic instability

2021 ◽  
Vol 2 (3) ◽  
pp. 695-712
Author(s):  
Kristine Flacké Haualand ◽  
Thomas Spengler
Keyword(s):  
Potential Vorticity ◽  
Wind Shear ◽  
Lower Stratosphere ◽  
Prediction Models ◽  
Weather Prediction ◽  
Baroclinic Instability ◽  
Polar Vortex ◽  
Dominant Factor ◽  
Latent Heating ◽  
The Impact

Abstract. Misrepresentations of wind shear and stratification around the tropopause in numerical weather prediction models can lead to errors in potential vorticity gradients with repercussions for Rossby wave propagation and baroclinic instability. Using a diabatic extension of the linear quasi-geostrophic Eady model featuring a tropopause, we investigate the influence of such discrepancies on baroclinic instability by varying tropopause sharpness and altitude as well as wind shear and stratification in the lower stratosphere, which can be associated with model or data assimilation errors or a downward extension of a weakened polar vortex. We find that baroclinic development is less sensitive to tropopause sharpness than to modifications in wind shear and stratification in the lower stratosphere, where the latter are associated with a net change in the vertical integral of the horizontal potential vorticity gradient across the tropopause. To further quantify the relevance of these sensitivities, we compare these findings to the impact of including mid-tropospheric latent heating. For representative modifications of wind shear, stratification, and latent heating intensity, the sensitivity of baroclinic instability to tropopause structure is significantly less than that to latent heating of different intensities. These findings indicate that tropopause sharpness might be less important for baroclinic development than previously anticipated and that latent heating and the structure in the lower stratosphere could play a more crucial role, with latent heating being the dominant factor.

The impact of sudden stratospheric warmings (SSWs) on UTLS composition, local radiative effects and air quality

2020 ◽  
Author(s):  
Ryan Williams ◽  
Michaela Hegglin ◽  
Patrick Jöckel ◽  
Hella Garny ◽  
Keith Shine ◽  
...  
Keyword(s):  
Air Quality ◽  
Atmospheric Chemistry ◽  
Large Scale ◽  
Lower Stratosphere ◽  
Weather Prediction ◽  
Onset Date ◽  
Identification Algorithm ◽  
Heating Rates ◽  
Transport Pathways ◽  
The Impact

<p>Midwinter sudden stratospheric warmings (SSWs), characterised by the reversal of the temperature gradient poleward of 60°N and the 10 hPa climatological zonal mean wind from westerly to easterly at 60°N, are known to have pronounced impacts on tropospheric circulation which lead to regional changes in temperature, precipitation and other meteorological variables. Such abrupt events are furthermore known to be associated with large-scale changes in the distribution of stratospheric chemistry constituents, such as ozone (O<sub>3</sub>) and water vapour (H<sub>2</sub>O), although the implications for stratosphere-troposphere exchange (STE) have not been previously investigated. The evolution of O<sub>3</sub> and H<sub>2</sub>O anomalies during an SSW life cycle are first examined from the surface up to 1 hPa using specified-dynamics simulations from the European Centre for Medium-Range Weather Forecasts – Hamburg (ECHAM)/Modular Earth Submodel System (MESSy) Atmospheric Chemistry (EMAC) model over the period 1979-2013. We show that significant positive anomalies in O<sub>3</sub> occur around the onset of an SSW in the middle to lower stratosphere, with persistence timescales of around 50 days in the upper troposphere-lower stratosphere (UTLS). Similarly, we find significant H<sub>2</sub>O anomalies in the lowermost stratosphere (± 25 %) for up to 75 days. The extent and magnitude of the anomalies are largely confirmed in both Copernicus Atmospheric Monitoring Service (CAMS) reanalysis and ozonesonde measurements at five different Arctic stations. These chemical perturbations result in local temperature changes of up to 2 K, which may impact numerical weather prediction (NWP) of the tropospheric response to SSWs. Evaluation of the vertical residual velocity (w*) support the notion of transport changes being the driver of the temporal evolution of the anomalies. Using a stratospheric-tagged O<sub>3</sub> tracer, a signal for enhanced STE of ozone is subsequently inferred (~ 5-10 %), which is maximised around 50 days after the SSW onset date. We furthermore attempt to elucidate STE transport pathways using a tropopause fold identification algorithm applied to ERA-Interim during this period, and assess such changes in folding frequency and distribution during such events. Our results highlight that SSWs can induce significantly disturbed O<sub>3</sub> and H<sub>2</sub>O distributions in the UTLS, leading to enhanced STE of O<sub>3</sub>, with potentially significant implications for radiative fluxes, atmospheric heating rates and air quality.</p>

scholarly journals Processing and quality control with FY-3C/GNOS data used in numerical weather prediction applications

2018 ◽  
Author(s):  
Mi Liao ◽  
Sean Healy ◽  
Peng Zhang
Keyword(s):  
Quality Control ◽  
Numerical Weather Prediction ◽  
Weather Prediction ◽  
Weather Forecasts ◽  
Numerical Weather ◽  
Noise Estimate ◽  
Ionosphere Model ◽  
Angle Space ◽  
Prediction Systems ◽  
L1 And L2

Abstract. The Chinese radio occultation sounder GNOS (Global Navigation Occultation Sounder) is on the FY-3C satellite, which was launched on September 23, 2013. Currently, GNOS data is transmitted via the Global Telecommunications System (GTS) providing 450–500 profiles per day for numerical weather prediction applications. This paper describes the processing for the GNOS profiles with large biases, related to L2 signal degradation. A new extrapolation procedure in bending angle space corrects the L2 bending angles, using a thin ionosphere model, and the fitting relationship between L1 and L2. We apply the approach to improve the L2 extrapolation of GNOS. The new method can effectively eliminate about 90 % of the large departures. In addition to the procedure for the L2 degradation, this paper also describes our quality control (QC) for FY-3C/GNOS. A noise estimate for the new L2 extrapolation can be used as a QC parameter to evaluate the performance of the extrapolation. Mean phase delays of L1 and L2 in the tangent height interval of 60 to 80 km are analysed and applied in the QC as well. A statistical comparison between GNOS and ECMWF (European Centre for Medium-Range Weather Forecasts) forecast data demonstrates that GNOS performs almost as well as GRAS, especially in the core region from around 10 to 35 km. The GNOS data with the new L2 extrapolation is suitable for assimilation into numerical weather prediction systems.

The impact of vertical resolution on tropical cyclone simulation

2020 ◽  
Author(s):  
Wei Huang ◽  
Mengjuan Liu ◽  
Xu Zhang ◽  
Jian-wen Bao
Keyword(s):  
Tropical Cyclone ◽  
Prediction Models ◽  
Weather Prediction ◽  
Vertical Mixing ◽  
Forecast Model ◽  
Horizontal Resolution ◽  
Model Solution ◽  
Vertical Resolution ◽  
Solution Convergence ◽  
The Impact

<p>It is well known that horizontal resolution has a great deal of impact on tropical cyclone simulations using numerical weather prediction models.  It is relatively less discussed in the literature how vertical resolution affects the solution convergence of tropical cyclone simulations.  In this study, the resolved kinetic energy spectrum, the Richardson number probability density function and resolved flow features are used as metrics to examine the behavior of solution convergence in tropical cyclone simulations using the Weather and Forecast Model (WRF).  It is found that for convective-scale simulations of a real tropical cyclone case with 3-km horizontal resolution, the model solution does not converge until a vertically stretched vertical resolution approaches 200 layers or more.  The results from this study confirm the results from a few previous studies that the subgrid turbulent mixing, particularly, the vertical mixing, plays a significant role in the behavior of model solution convergence with respect to vertical resolution.  They also provide a basis for the vertical grid configuration selection for the operational tropical cyclone model of Shanghai Meteorological Service.</p>

scholarly journals Downward Control from the Lower Stratosphere?

2005 ◽  
Vol 62 (10) ◽  
pp. 3808-3817 ◽  
Author(s):  
Joseph Egger ◽  
Klaus-Peter Hoinka
Keyword(s):  
Angular Momentum ◽  
Lower Stratosphere ◽  
Meridional Circulation ◽  
Momentum Exchange ◽  
Weather Forecasts ◽  
Tropospheric Circulation ◽  
Control Concept ◽  
Highly Correlated ◽  
The Tropics ◽  
The Impact

Abstract The concept of downward control proposes a mechanism for the impact of the stratospheric circulation on the troposphere. Momentum forcing at upper-stratospheric levels induces a meridional circulation that eventually reaches the surface. So far, a lack of sufficiently accurate data hindered an observational test of this downward propagation. The concept is extended in this paper by looking at the effect of angular momentum forcing in prescribed regions in the lower stratosphere on the tropospheric circulation. In that case, the European Centre for Medium-Range Weather Forecasts Reanalysis Project (ERA) data can be used to investigate the atmospheric response to forcing in a prescribed domain. It is found that these forcing events are quite short lived and that angular momentum flux convergence in the prescribed domain is highly correlated with convergence outside this forcing area. Typically, these fields of convergence and also divergence extend to the surface in a quasibarotropic manner outside the Tropics. This structure of the forcing is not compatible with the assumptions of the downward control concept. The observed related meridional circulation therefore differs widely from that predicted. In particular, there is no obvious descent of the circulation to the ground. Even so, such forcing events are accompanied by an intensive exchange of angular momentum between stratosphere and troposphere. The confinement of the forcing to the selected forcing domain is reasonably strict in the Tropics. A relatively narrow tongue of angular momentum is growing at the equator underneath the forcing area. Frictional torques play a role in this development. Altogether, the forcing events as selected involve a strong angular momentum exchange between stratosphere and troposphere but are not suited for a test of the downward control concept. Alternatives are discussed.

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