The NCEP Climate Forecast System Reanalysis (CFSR) was completed for the 31-yr period from 1979 to 2009, in January 2010. The CFSR was designed and executed as a global, high-resolution coupled atmosphere–ocean–land surface–sea ice system to provide the best estimate of the state of these coupled domains over this period. The current CFSR will be extended as an operational, real-time product into the future. New features of the CFSR include 1) coupling of the atmosphere and ocean during the generation of the 6-h guess field, 2) an interactive sea ice model, and 3) assimilation of satellite radiances by the Gridpoint Statistical Interpolation (GSI) scheme over the entire period. The CFSR global atmosphere resolution is ~38 km (T382) with 64 levels extending from the surface to 0.26 hPa. The global ocean's latitudinal spacing is 0.25° at the equator, extending to a global 0.5° beyond the tropics, with 40 levels to a depth of 4737 m. The global land surface model has four soil levels and the global sea ice m...

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The NCEP Climate Forecast System Reanalysis

The purpose of this paper is to provide a comprehensive presentation and interpretation of the Ensemble Kalman Filter (EnKF) and its numerical implementation. The EnKF has a large user group, and numerous publications have discussed applications and theoretical aspects of it. This paper reviews the important results from these studies and also presents new ideas and alternative interpretations which further explain the success of the EnKF. In addition to providing the theoretical framework needed for using the EnKF, there is also a focus on the algorithmic formulation and optimal numerical implementation. A program listing is given for some of the key subroutines. The paper also touches upon specific issues such as the use of nonlinear measurements, in situ profiles of temperature and salinity, and data which are available with high frequency in time. An ensemble based optimal interpolation (EnOI) scheme is presented as a cost-effective approach which may serve as an alternative to the EnKF in some applications. A fairly extensive discussion is devoted to the use of time correlated model errors and the estimation of model bias.

The Ensemble Kalman Filter: Theoretical formulation and practical implementation

[1] Observations of temperature, winds, and atmospheric trace gases suggest that the transition from troposphere to stratosphere occurs in a layer, rather than at a sharp “tropopause.” In the tropics, this layer is often called the “tropical tropopause layer” (TTL). We present an overview of observations in the TTL and discuss the radiative, dynamical, and chemical processes that lead to its time-varying, three-dimensional structure. We present a synthesis definition with a bottom at 150 hPa, 355 K, 14 km (pressure, potential temperature, and altitude) and a top at 70 hPa, 425 K, 18.5 km. Laterally, the TTL is bounded by the position of the subtropical jets. We highlight recent progress in understanding of the TTL but emphasize that a number of processes, notably deep, possibly overshooting convection, remain not well understood. The TTL acts in many ways as a “gate” to the stratosphere, and understanding all relevant processes is of great importance for reliable predictions of future stratospheric ozone and climate.

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Tropical tropopause layer

Regional climate modeling using convection-permitting models (CPMs; horizontal grid spacing 10 km). CPMs no longer rely on convection parameterization schemes, which had been identified as a major source of errors and uncertainties in LSMs. Moreover, CPMs allow for a more accurate representation of surface and orography fields. The drawback of CPMs is the high demand on computational resources. For this reason, first CPM climate simulations only appeared a decade ago. In this study, we aim to provide a common basis for CPM climate simulations by giving a holistic review of the topic. The most important components in CPMs such as physical parameterizations and dynamical formulations are discussed critically. An overview of weaknesses and an outlook on required future developments is provided. Most importantly, this review presents the consolidated outcome of studies that addressed the added value of CPM climate simulations compared to LSMs. Improvements are evident mostly for climate statistics related to deep convection, mountainous regions, or extreme events. The climate change signals of CPM simulations suggest an increase in flash floods, changes in hail storm characteristics, and reductions in the snowpack over mountains. In conclusion, CPMs are a very promising tool for future climate research. However, coordinated modeling programs are crucially needed to advance parameterizations of unresolved physics and to assess the full potential of CPMs.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1002/2014RG000475

A review on regional convection-permitting climate modeling: Demonstrations, prospects, and challenges.

The radio occultation (RO) technique, which makes use of radio signals transmitted by the global positioning system (GPS) satellites, has emerged as a powerful and relatively inexpensive approach for sounding the global atmosphere with high precision, accuracy, and vertical resolution in all weather and over both land and ocean. On 15 April 2006, the joint Taiwan-U.S. Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC)/Formosa Satellite Mission 3 (COSMIC/FORMOSAT-3, hereafter COSMIC) mission, a constellation of six microsatellites, was launched into a 512-km orbit. After launch the satellites were gradually deployed to their final orbits at 800 km, a process that took about 17 months. During the early weeks of the deployment, the satellites were spaced closely, offering a unique opportunity to verify the high precision of RO measurements. As of September 2007, COSMIC is providing about 2000 RO soundings per day to support the research and operational communities. COSMIC RO dat...

/pdf/the-cosmic-formosat-3-mission-early-results-2bn1owr3dc.pdf

The COSMIC/FORMOSAT-3 Mission: Early Results

The first radio occultation measurements of the CHAMP (CHAllenging Minisatellite Payload) satellite using Global Positioning System (GPS) signals have been performed on February 11, 2001. By the end of April 2001 more than 3000 occultations were recorded. Globally distributed vertical profiles of dry temperature and specific humidity are derived, of which a set of 438 vertical dry temperature profiles is compared with corresponding global weather analyses. The observed temperature bias is less than ∼1 K above the tropopause and even less than 0.5 K in the altitude interval from 12 to 20 km at latitudes >30°N. About 55% of the compared profiles reached the last kilometer above the Earth's surface. In spite of the activated anti-spoofing mode of the GPS system the state-of-the-art GPS flight receiver aboard CHAMP combined with favorable antenna characteristics allows for atmospheric sounding with high accuracy and vertical resolution.

/pdf/atmosphere-sounding-by-gps-radio-occultation-first-results-47ul56v4i1.pdf

Atmosphere sounding by GPS radio occultation: First results from CHAMP

The world of satellite navigation is undergoing dramatic changes with the rapid development of multi-constellation Global Navigation Satellite Systems (GNSSs). At the moment more than 70 satellites are already in view, and about 120 satellites will be available once all four systems (BeiDou + Galileo + GLONASS + GPS) are fully deployed in the next few years. This will bring great opportunities and challenges for both scientific and engineering applications. In this paper we develop a four-system positioning model to make full use of all available observations from different GNSSs. The significant improvement of satellite visibility, spatial geometry, dilution of precision, convergence, accuracy, continuity and reliability that a combining utilization of multi-GNSS brings to precise positioning are carefully analyzed and evaluated, especially in constrained environments.

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Precise positioning with current multi-constellation Global Navigation Satellite Systems: GPS, GLONASS, Galileo and BeiDou

Orbit and Earth Gravity Field.- Ice Mass Balance and Antarctic Gravity Change: Satellite and Terrestrial Perspectives.- Gravity Model TUM-2Sp Based on the Energy Balance Approach and Kinematic CHAMP Orbits.- On the Contribution of CHAMP to Temporal Gravity Field Variation Studies.- Earth Gravity Field and Seasonal Variability from CHAMP.- Comparison of Superconducting Gravimeter and CHAMP Satellite Derived Temporal Gravity Variations.- Improvements in Arctic Gravity and Geoid from CHAMP and GRACE: An Evaluation.- Evaluation of Gravity Data by EIGEN-2 (CHAMP-only) Model in China.- Energy Balance Relations for Validation of Gravity Field Models and Orbit Determinations Applied to the CHAMP Mission.- Evaluation of Terrestrial Gravity Data by Independent Global Gravity Field Models.- Recent Developments in CHAMP Orbit Determination at GFZ.- On Calibrating the CHAMP On-Board Accelerometer and Attitude Quaternion Processing.- Evaluation of the CHAMP Accelerometer on Two Years of Mission.- A New Method to Detect and Estimate CHAMP Clock Bias Change Cycle Slip.- Comparison of Different Stochastic Orbit Modeling Techniques.- Determination of Non-Conservative Accelerations from Orbit Analysis.- CHAMP and Resonances.- CHAMP Gravity Field Solutions and Geophysical Constraint Studies.- Application of Eigenvalue Decomposition in the Parallel Computation of a CHAMP 100x100 Gravity Field.- Time-Variable Gravity Seen by Satellite Missions: On its Sampling and its Parametrization.- Gravity Field Recovery by Analysis of Short Arcs of CHAMP.- Statistical Assessment of CHAMP Data and Models Using the Energy Balance Approach.- Multiscale Geopotential Solutions from CHAMP Orbits and Accelerometry.- Multiscale Modeling from EIGEN-1S, EIGEN-2, EIGEN-GRACE01S, UCPH2002_0.5, EGM96.- A Comparison of Various Procedures for Global Gravity Field Recovery from CHAMP Orbits.- Precise Orbit Determination for CHAMP Using an Efficient Kinematic and Reduced-Dynamic Procedure.- On Bias and Scale and Thrust Factors for CHAMP Accelerometry.- CHAMP Accelerometer Preprocessing at GeoForschungsZentrum Potsdam.- CHAMP Clock Characterization Revisited.- How Baltic Sea Water Mass Variations Mask the Postglacial Rebound Signal in CHAMP and GRACE Gravity Field Solutions.- The Impact of the New CHAMP and GRACE Gravity Models on the Measurement of the General Relativistic Lense-Thirring Effect.- Recovery of Isostatic Topography over North America from Topographic and CHAMP Gravity Correlations.- Dynamic Topography as Reflected in the Global Gravity Field.- Impact of the CHAMP Mission on Estimating the Mean Sea Surface.- Improved Estimates of the Oceanic Circulation Using the CHAMP Geoid.- Contemporary Changes in the Geoid About Greenland: Predictions Relevant to Gravity Space Missions.- Mantle Viscosity and S-Wave to Density Conversion Profiles using CHAMP Geoid Data.- Regional Geoid Undulations from CHAMP, Represented by Locally Supported Basis Functions.- Earth Magnetic Field.- Ionospheric Plasma Effects for Geomagnetic LEO Missions at Mid- and Low-Latitudes.- Interpretation of CHAMP Crustal Field Anomaly Maps Using Geographical Information System (GIS) Technique.- Magnetic Crustal Thickness in Greenland from CHAMP and Orsted Data.- CHAMP Magnetic Anomalies of the Antarctic Crust.- Magnetic Petrology Database for Interpretation Satellite Magnetic Anomalies.- Balloon Geomagnetic Survey at Stratospheric Altitudes.- Effect of Varying Crustal Thickness on CHAMP Geopotential Data.- Reliability of CHAMP Anomaly Continuations.- Introducing POMME, the POtsdam Magnetic Model of the Earth.- Alternative Parameterisations of the External Magnetic Field and its Induced Counterpart for 2001 and 2002 Using Orsted, Champ and Observatory Data.- New Insight into Secular Variation Between MAGSAT and CHAMP/ORSTED.- Time Structure of the 1991 Magnetic Jerk in the Core-Mantle Boundary Zone by Inverting Global Magnetic Data Supported by Satellite Measurements.- Use of Champ Magnetic Data to Improve the Antarctic Geomagnetic Reference Model.- Secular Variation of the Geomagnetic Field from Satellite Data.- The Spectrum of the Magnetic Secular Variation.- Geomagnetic Induction Modeling Based on CHAMP Magnetic Vector Data.- Electromagnetic Induction by Sq Ionospheric Currents in a Heterogeneous Earth: Modeling Using Ground-based and Satellite Measurements.- Wavelet Analysis of CHAMP Flux Gate Magnetometer Data.- Modelling the Ocean Effect of Geomagnetic Storms at Ground and Satellite Altitude.- 3-D Modelling of the Magnetic Fields Due to Ocean Tidal Flow.- The Enhancement of the Thermospheric Density During the Sept. 25-26, 2001 Magnetic Storm.- On the Modelling of Field-Aligned Currents from Magnetic Observations by Polar Orbiting Satellites.- The Low-Altitude Cusp: Multi-Point Observations During the February 2002 SIRCUS Campaign.- Detection of Intense Fine-Scale Field-Aligned Current Structures in the Cusp Region.- A Comparative Study of Geomagnetic Pi2 Pulsations Observed by CHAMP and on the Ground.- ULF Wave Magnetic Measurements by CHAMP Satellite and SEGMA Ground Magnetometer Array: Case Study of July 6, 2002.- Classes of the Equatorial Electrojet.- The ESPERIA Project: a Mission to Investigate the near-Earth Space.- Status of the CHAMP ME Data Processing.- Neutral Atmosphere and Ionosphere.- Atmospheric and Ocean Sensing with GNSS.- Amplitude Variations in CHAMP Radio Occultation Signal as an Indicator of the Ionospheric Activity.- About the Potential of GPS Radio Occultation Measurements for Exploring the Ionosphere.- Validation of GPS Ionospheric Radio Occultation results onboard CHAMP by Vertical Sounding Observations in Europe.- Ionospheric Tomography with GPS Data from CHAMP and SAC-C.- Topside Plasma Scale Height Modelling Based on CHAMP Measurements: First Results.- Differential Code Bias of GPS Receivers in Low Earth Orbit: An Assessment for CHAMP and SAC-C.- Ionosphere/Plasmasphere Imaging Based on GPS Navigation Measurements from CHAMP and SAC-C.- Three-Dimensional Monitoring of the Polar Ionosphere with Ground- and Space-Based GPS.- Comparison of Electron Density Profiles from CHAMP Data with NeQuick Model.- Model for Short-term Atmospheric Density Variations.- Atmospheric Profiling with CHAMP: Status of the Operational Data Analysis, Validation of the Recent Data Products and Future Prospects.- Simulated Temperature and Water Vapor Retrieval from Bending Angles and Refractivity Measurements using an Optimal Estimation Approach.- An Analysis of the Lower Tropospheric Refractivity Bias by Heuristic Sliding Spectral Methods.- Diffractive Integrals for Bistatic Remote Sensing Using GPS Signals.- Canonical Transform Methods for Analysis of Radio Occultations.- GPS Radio Occultation with CHAMP: Comparison of Atmospheric Profiles from GFZ Potsdam and IGAM Graz.- Evaluation of Stratospheric Radio Occultation Retrieval Using Data from CHAMP, MIPAS, GOMOS, and ECMWF Analysis Fields.- Derivation of the Water Vapor Content from the GNSS Radio Occultation Observations.- Processing of CHAMP Radio Occultation Data Using GRAS SAF Software.- Gravity Wave "Portrait" Reconstructed by Radio Holographic Analysis of the Amplitude of GPS Radio Occultation Signals.- Global Analysis of Stratospheric Gravity Wave Activity Using CHAMP Radio Occultation Temperatures.- Tropical Tropopause Characteristics from CHAMP.- Comparisons of MIPAS/ENVISAT and GPS-RO/CHAMP Temperatures.- Comparison of GPS/SAC-C and MIPAS/ENVISAT Temperature Profiles and Its Possible Implementation for EOS MLS Observations.- Structure and Variability of the Tropopause Obtained from CHAMP Radio Occultation Temperature Profiles.- An Assessment of an Ionospheric GPS Data Assimilation Process.- The Continuous Wavelet Transform, a Valuable Analysis Tool to Detect Atmospheric and Ionospheric Signatures in GPS Radio Occultation Phase Delay Data.- The CHAMP Atmospheric Processing System for Radio Occultation Measurements.- Potential Contribution of CHAMP Occultation to Pressure Field Improvement for Gravity Recovery.- Analysis of Gravity Wave Variability from SAC-C and CHAMP Occultation Profiles between June 2001 and March 2003.- The CHAMPCLIM Project: An Overview.

Earth Observation with CHAMP Results from Three Years in Orbit

[1] GPS radio occultation measurements from CHAMP, GRACE-A and FORMOSAT-3/COSMIC are used to derive global information on small-scale ionospheric irregularities such as sporadic E layers between January 2002 and December 2007. The investigations are based on the analysis of amplitude variations of the GPS radio occultation signals. The global distribution of ionospheric irregularities shows strong seasonal variations with highest occurrence rates during summer in the middle latitudes. The long-term data set of CHAMP allows for first climatological studies, while the data coverage increases significantly with the combination of CHAMP, GRACE and FORMOSAT-3/COSMIC measurements. This allows for global maps of sporadic E occurrence rates of very high spatial resolution where the influence of the Earth's magnetic field becomes visible in global sporadic E maps for the first time.

A global climatology of ionospheric irregularities derived from GPS radio occultation

http://radiometrics.com/data/uploads/2013/04/Bender_ASR_11.pdf

Jens Wickert

Papers

Atmosphere sounding by GPS radio occultation: First results from CHAMP

Precise positioning with current multi-constellation Global Navigation Satellite Systems: GPS, GLONASS, Galileo and BeiDou

Earth Observation with CHAMP Results from Three Years in Orbit

A global climatology of ionospheric irregularities derived from GPS radio occultation

Development of a GNSS water vapour tomography system using algebraic reconstruction techniques