Determining the likely localization of methane sources using forecast time series and satellite data

The paper is devoted to the topical problem of determining the sources of methane from observational data. An algorithm based on the statistical optimization method used to estimate a time constant parameter is considered. To implement the algorithm, a variant of ensemble smoothing is used, which is an optimal estimate of the desired parameter based on observational data and forecast for a given time interval. This paper presents the implementation of the algorithm for real observational and forecast data, the results of a three-dimensional transport and diffusion model are taken as a mathematical model, and satellite measurement data are used as observational data. Methane fluxes are estimated in subdomains of the Earth’s surface for specified time intervals. The paper contains a mathematical formulation of the problem, a scheme for its numerical implementation. The results of numerical experiments with model and real data are presented.

Performance Analysis and Validation of Precision Multisatellite RF Measurement Scheme for Microsatellite Formations

Almost all existing studies on inter-satellite radio frequency (RF) measurement have focused on two-satellite formations. Although some frequency division multiple access and code division multiple access multisatellite RF measurement schemes have been proposed, their poor scalability does not satisfy the inter-satellite measurement requirements of multisatellite formations, especially large-scale formations. Two-way ranging (TWR), which is based on a time division mechanism, is an effective solution that has been used for inter-satellite links in the global positioning system and Beidou navigation constellations. However, the high measurement accuracy achieved with TWR in these navigation constellations is heavily reliant on high-performance atomic clocks and the assistance of navigation ephemeris, which are not available on microsatellite platforms. This work focuses on a scalable multisatellite measurement scheme that adopts a distributed broadcast-based time division multiple access mechanism as the media access control layer and uses an asymmetric double-side TWR method as the physical layer. The measurement performance of the proposed scheme is evaluated through in-depth theoretical modeling, simulation verification, and experimental validation, along with a comprehensive comparison with the conventional TWR method. The experimental results show that centimeter-level measurement accuracy can be achieved with the proposed scheme when only a common miniaturized frequency source is used. This accuracy level is two orders of magnitude better than that of the TWR method, and thus satisfies the application requirements of general large-scale microsatellite formations.

Sea surface salinity short-term variability in the tropics

Using data from the Global Tropical Moored Buoy Array, we study the validation process for satellite measurement of sea surface salinity (SSS). We compute short-term variability (STV) of SSS, variability on timescales of 2–17 d. It is a proxy for subfootprint variability over a 100 km footprint as seen by a satellite measuring SSS. We also compute representation error, which is meant to mimic the SSS satellite validation process where footprint averages are compared to pointwise in situ values. We present maps of these quantities over the tropical array. We also look at seasonality in the variability of SSS and find which months have maximum and minimum amounts. STV is driven at least partly by rainfall. Moorings exhibit larger STV during rainy periods than during non-rainy ones. The same computations are also done using output from a high-resolution global ocean model to see how it might be used to study the validation process. The model gives good estimates of STV, in line with the moorings, although tending to have smaller values.

Sea Surface Salinity Short Term Variability in the Tropics

Using data from the Global Tropical Moored Buoy Array we study the validation process for satellite measurement of sea surface salinity (SSS). We compute short-term variability (STV) of SSS, variability on time scales of 5–14 days. It is meant to be a proxy for subfootprint variability as seen by a satellite measuring SSS. We also compute representation error, which is meant to mimic the SSS satellite validation process where footprint averages are compared to pointwise in situ values. We present maps of these quantities over the tropical array. We also look at seasonality in the variability of SSS and find which months have maximum and minimum amounts. STV is driven at least partly by rainfall. Moorings exhibit larger STV during rainy periods than non-rainy ones. The same computations are also done using output from a high-resolution global ocean model to see how it might be used to study the validation process. The model gives good estimates of STV, in line with the moorings, though tending to have smaller values.

Site selection for solar photovoltaic system installation using analytical hierarchy process model in Azerbaijan

The most suitable sites for solar photovoltaic power installations are determined through a comprehensive assessment of the meteorological, economic and environmental criteria of the energy potential areas. The basic criteria for location selection are evaluated using an analytical hierarchy process method based on multi-criteria decision-making technique for large-scale solar photovoltaic projects. The analytical hierarchy process model is also applied to evaluate areas of high solar potential and factors that are primary criteria for determinate the site suitability index modelling. This method considers various conditions, such as production and technological considerations, which aim to maximise the short-term profit from the project and the efficiency of power generation. In the study, a consistency ratio of suitable localities was determined and proper alternatives for the construction of photovoltaic installations were evaluated. In addition to local meteorology and related satellite measurement data, the country’s radiation values also were compared by converting a digital elevation model data using the tool «Area solar radiation» in GIS. As a result of calculating the site suitability index with the ArcGIS weighted overlay tool, it was concluded that 1.17 % (1016.8 km2) of the country are the most suitable sites for the installation of solar PV systems. These areas mainly include Khizi, Gobustan, Hajigabul, Beylagan, Sharur, Babek and Jeyranchol zones. The total number of locations identified accross the country, classified into 3 categories according to their level of suitability, includes 40 sites. Eight of these high suitability sites, all in Nakhchivan Autonomous Republic, contain 11 % (109.2 km2) of the total potential area. The remaining 32 sites, corresponding to areas with medium and low energy potential, cover 28 % (284.6 km2) and 61 % (623 km2), respectively. When these areas are completely covered with PV panels, it will be possible to fully supply the energy demand of the country with solar energy.

Multi-Satellite Relative Navigation Scheme for Microsatellites Using Inter-Satellite Radio Frequency Measurements

The inter-satellite relative navigation method—based on radio frequency (RF) range and angle measurements—offers good autonomy and high precision, and has been successfully applied to two-satellite formation missions. However, two main challenges occur when this method is applied to multi-microsatellite formations: (i) the implementation difficulty of the inter-satellite RF angle measurement increases significantly as the number of satellites increases; and (ii) there is no high-precision, scalable RF measurement scheme or corresponding multi-satellite relative navigation algorithm that supports multi-satellite formations. Thus, a novel multi-satellite relative navigation scheme based on inter-satellite RF range and angle measurements is proposed. The measurement layer requires only a small number of chief satellites, and a novel distributed multi-satellite range measurement scheme is adopted to meet the scalability requirement. An inter-satellite relative navigation algorithm for multi-satellite formations is also proposed. This algorithm achieves high-precision relative navigation by fusing the algorithm and measurement layers. Simulation results show that the proposed scheme requires only three chief satellites to perform inter-satellite angle measurements. Moreover, with the typical inter-satellite measurement accuracy and an inter-satellite distance of around 1 km, the proposed scheme achieves a multi-satellite relative navigation accuracy of ~30 cm, which is about the same as the relative navigation accuracy of two-satellite formations. Furthermore, decreasing the number of chief satellites only slightly degrades accuracy, thereby significantly reducing the implementation difficulty of multi-satellite RF angle measurements.

Extreme Ice Crystal Events Linked to Biomass and Fossil Fuel Combustion

Eight years of upper tropospheric (UT) ice crystal measurements with the Backscatter Cloud Probe (BCP), operated as part of the In-Service Aircraft for a Global Observing System (IAGOS), have been analyzed to assess the frequency and characteristics of extreme ice crystal events (EIE), defined in this study as encounters with clouds that have number concentrations exceeding 5000 L−1. A total of 6490 events, in clouds of horizontal extent ≥ 2.5 km, were identified during the period from December 2011 to March 2020 in the global band between 30° S and 30° N. Evaluation of in situ measurements of carbon monoxide in these UT clouds, combined with back-trajectories and carbon monoxide emission inventories, allow the identification of regional anthropogenic sources. An evaluation of low- and upper-level kinematic variables from the Modern-Era Retrospective analysis for Research and Applications, Version 2 (MERRA-2), combined with spatial distribution of aerosol optical depth and regions of biomass burning, reveal the physical mechanism by which the particles are lofted to flight levels in regions of deep convection. The maps of lightning frequency derived from the World Wide Lightning Location Network (WWLLN) contribute additional evidence of the role of deep convection lofting ice forming aerosols to the UT. The MERRA-2 analysis shows clear spatial correlations that link dust, black carbon (BC), organic carbon (OC) and sulfate particles with regions of EIE. Given the composition of the source aerosols and the nature of their transport to the UT, the ice clouds are likely of liquid origin whereby droplets formed on these particles are lofted and freeze heterogeneously as have been reported in previous studies. The results from this study have important ramifications related to climate change, satellite measurement validation, weather forecasting and aircraft operations.

Improving Spatial Coverage of Satellite Aerosol Classification Using a Random Forest Model

The spatial coverage of satellite aerosol classification was improved using a random forest (RF) model trained with observational data including target (aerosol type) and input (satellite measurement) variables. The AErosol RObotic NETwork (AERONET) aerosol-type dataset was used for the target variables. Satellite input variables with many missing data or low mean-decrease accuracy were excluded from the final input variable set, and good performance in aerosol-type classification was achieved. The performance of the RF-based model was evaluated on the basis of the wavelength dependence of single-scattering albedo (SSA) and fine-mode-fraction values from AERONET. Typical SSA wavelength dependence for individual aerosol types was consistent with that obtained for aerosol types by the RF-based model. The spatial coverage of the RF-based model was also compared with that of previously developed models in a global-scale case study. The study demonstrates that the RF-based model allows satellite aerosol classification with improved spatial coverage, with a performance similar to that of previously developed models.

Evaluation of Pendulum NGGM Scenarios by Full Closed-Loop Simulation

<p>The GRACE mission (2002-2017) delivered temporal gravity field solutions of the Earth for 15 years. It's successor, GRACE follow-on (GRACE-FO) is continuing it's legacy since May 2018. The time series of monthly gravity fields revealed global mass redistribution in in the near surface layer of the Earth with unprecedented accuracy. This assessed a completely new observable in geoscience disciplines and has become a crucial data product for climate research.<br>Despite the groundbreaking success and relevance of the GRACE mission(s) for Earth observation and climate science, no further successor gravity mission is planned, yet. Summarized by the name Next Generation Gravity Mission (NGGM) concepts for future gravimetry missions have been proposed and analyzed for a while. As an outcome of these studies the so called Bender-configuration (two GRACE-like satellite pairs, one in a polar orbit and a second in an inclined orbit around 60° to 70°) is the concept currently favored by the scientific community for a candidate of the next gravity mission to be realized.</p><p><br>However, an other concept still remains interesting due to specific advantages that might contribute to future improvements of gravity missions. In order to emphasize this, we present results of a full closed loop-simulation for a different ll-SST approach, the so called pendulum. It offers a quite similar overall performance with just two satellites. For this configuration the satellites are following each other in orbits with slightly different longitudes of the ascending nodes, thus the inter-satellite measurement direction is varying between along-track and cross-track. This configuration makes an interferometric laser ranging (LRI) quite challenging on the technical level. Nevertheless, the LRI accuracy is not necessarily needed. The relevance of the pendulum configuration has also been shifted into the focus of the French MARVEL mission proposal.</p><p><br>In this contribution we analyze in detail the performance of the pendulum formation with the main parameters being the angle between along-track and cross-track component of the ranging direction at the equator, and the mean distance between the satellites. We conduct the angle variation for different mean ranges and assumed ranging accuracies. As reference, the GRACE and Bender concepts are simulated, as well. The orbit simulations are performed using a derivative of the ZARM/DLR XHPS mission simulator including high precision implementations of non-gravitational accelerations.<br>The different concepts and configurations include complete GRACE-FO like attitude control and realistic environment models. State-of-the-art instrument noise models based on GRACE/-FO are used to generate observation data for accelerometer (ACC), range dependent inter satellite ranging (KBR/LRI), kinematic orbit solution (KOS) and star camera (SCA). For the gravity recovery process we use the classical variational equation approach. As for real GRACE processing, ACC calibration parameter are estimated and KOS and KBR range-rate observations are weighted by VCE.</p>