Description: No abstract is available for this article.

Description: This paper is an update and extension of an earlier study of the centered and eccentric dipole models of the Earth's magnetic field [ Fraser-Smith , 1987]. We use the 1980–2015 IGRF Gauss coefficients to recalculate the magnetic dipole moments and pole positions for both the centered and eccentric dipoles for an additional 35 years. The changes that have taken place are mostly extensions of the trends described earlier. Interestingly, the earlier weak suggestion of an accelerated decline in the magnetic moment over the interval 1975–1985 persists in the more recent data; if the current decline for the years 2000–2015 continues, the Earth's field is projected to decline to nothing around the year 3797 AD. This projected decline to zero field will almost certainly not occur on this date but it is of interest because the time scale for the decline is remarkably short compared with the time scales derived for past field reversals. The asymmetry of the Earth's field continues to increase quite rapidly, with the offset of the equivalent dipole from the Earth's center now close to 9% of the Earth's radius. Since we now know that all the planets in our solar system with global magnetic fields have asymmetric fields that can be modeled more accurately as eccentric dipole fields, and not as centered dipole fields, the eccentric dipole analysis reported here can now be viewed more generally as an approach to planetary magnetic fields and not just to the magnetic field of our own planet.

Description: The El Niño Modoki in 2010 led to historic droughts in Brazil. In order to understand its impact on carbon cycle variability, we derive the 2011-2010 annual carbon flux change ( δ F ) globally and specifically to Brazil using the NASA Carbon Monitoring System Flux (CMS-Flux) framework. Satellite observations of CO 2 , CO, and solar induced fluorescence (SIF) are ingested into a 4D-variational assimilation system driven by carbon cycle models to infer spatially resolved carbon fluxes including net ecosystem production, biomass burning, and gross primary productivity (GPP). The global 2011-2010 net carbon flux change was estimated to be δ F = -1.60 PgC while the Brazilian carbon flux change was -0.24 ± 0.11 PgC. This estimate is broadly within the uncertainty of previous aircraft based estimates restricted to the Amazon basin. The 2011-2010 biomass burning change in Brazil was -0.24 ± 0.036 PgC, which implies a near-zero 2011-2010 change of the net ecosystem production (NEP): the near-zero NEP change is the result of quantitatively comparable increases GPP (0.31 ± 0.20 PgC) and respiration in 2011. Comparisons between Brazilian and global component carbon flux changes reveal complex interactions between the processes controlling annual land-atmosphere CO 2 exchanges. These results show the potential of multiple satellite observations to help quantify and spatially resolve the response of productivity and respiration fluxes to climate variability.

Description: We examine the middle atmospheric odd-hydrogen (HO x ) chemistry by comparing the Aura Microwave Limb Sounder (MLS) OH and HO 2 measurements with a photochemical model simulation. The model underestimates mesospheric OH and HO 2 concentrations if the standard chemical kinetic rates are used, whether the model H 2 O and O 3 are constrained with observations or not. To resolve the discrepancies, we adjust the kinetic rate coefficients of three key reactions (O + OH O 2 + H, OH + HO 2 H 2 O + O 2 , and H + O 2 + M HO 2 + M) and the O 2 photo absorption cross section at Lyman-α (121.57 nm) using the Bayesian optimal estimation. A much better model-observation agreement can be achieved if the kinetic rate coefficients for H + O 2 + M HO 2 + M is increased by 134–310%, and the O 2 photo absorption cross section at Lyman-α is reduced by 33–54%, while the kinetic rate coefficients for O + OH O 2 + H and OH + HO 2 H 2 O + O 2 remain consistent with the current laboratory values. The kinetic rate coefficient for H + O 2 + M HO 2 + M requires a very large adjustment beyond the uncertainty limits recommended in the NASA Data Evaluation, suggesting the need for future laboratory measurements. An alternative explanation is that the radiative association reaction, H + O 2 HO 2 + h ν, plays a significant role, which has never been measured. Our results demonstrate that high quality satellite observations can be used to constrain photochemical parameters and help improve our understanding of atmospheric chemistry.

Description: To better understand the variability of precipitation, circulation, and cloud, we examine the precipitation, vertical velocity, total cloud fraction, condensed water path, and ice water path from observations and 13 Coupled Model Intercomparison Project 5 (CMIP5) models over 1988-2008. All variables are averaged over wet areas and dry areas to investigate temporal variations of different variables over these regions. We found all models demonstrate similar temporal variations of precipitation as the observational data from the Global Precipitation Climatology Project, with positive trend over wet areas (6.22 ± 3.75 mm/mon/decade) and negative trend over dry areas (−0.77 ± 0.54 mm/mon/decade). Positive trends of vertical velocity, total cloud fraction, condensed water path, and ice water path are also found in the observations and models over the wet areas. Observations also demonstrate decreasing trends of vertical velocity, total clouds, condensed water path, ice water path over the dry areas, which can be simulated by most models with a few exceptions. The qualitatively consistent trends in these variables (i.e., vertical velocity, cloud, liquid and ice water contents) as revealed from the observations and CMIPS models provide a clearer picture of the dynamics and physics behind the temporal variations of precipitation over different areas.

Description: Atmospheric Infrared Sounder (AIRS) mid-tropospheric methane (CH 4 ) data is utilized to study the variation of methane concentrations over the Pacific Ocean with an emphasis on the correlation to El Niño Southern Oscillation (ENSO). When El Niño events happen, the rising air over the central Pacific can bring low surface concentrations of CH 4 over the ocean into mid-troposphere, resulting in a reduction of mid-tropospheric CH 4 over the region. On the contrary, the rising air over the western Pacific brings low surface CH 4 to the mid-troposphere during the La Nina events, which leads to negative mid-tropospheric CH 4 anomalies over the western Pacific. In the horizontal direction, there are stronger southward winds during El Niño than La Niña months in the region of the western Pacific Ocean. The stronger southward winds during El Niño can enhance the transport of high concentration CH 4 from the northern hemisphere to the tropical western Pacific region and contribute to the positive CH 4 anomalies over the region. The difference of mid-tropospheric CH 4 can reach +15 ppb (-15 ppb) over the western (central) Pacific between El Niño and La Niña events. The noteworthy difference of CH 4 has a significant correlation to the Southern Oscillation Index with a correlation coefficient of 0.74. The change in the transports associated with the ENSO event is an important factor for CH 4 anomalies in the middle troposphere. Results found in this study can help us better understand the spatio-temporal variability of methane.

Description: No abstract is available for this article.

Description: A factorial inferential grids grouping and representativeness analysis ( FIGGRA ) approach is developed to achieve a systematic selection of representative grids in large-scale climate change impact assessment and adaptation ( LSCCIAA ) studies and other fields of earth and space sciences. FIGGRA is applied to representative-grids selection for temperature ( Tas ) and precipitation ( Pr ) over the Loess Plateau ( LP ) to verify methodological effectiveness. FIGGRA is effective at and outperforms existing grid selection approaches (e.g. self-organizing maps) in multiple aspects such as clustering similar grids, differentiating dissimilar grids, and identifying representative grids for both Tas and Pr over LP . In comparison with Pr , the lower spatial heterogeneity and higher spatial discontinuity of Tas over LP leads to higher within-group similarity, lower between-group dissimilarity, lower grids grouping effectiveness, and higher grid representativeness; the lower inter-annual variability of the spatial distributions of Tas results in lower impacts of the inter-annual variability on the effectiveness of FIGGRA . For LP , the spatial climatic heterogeneity is the highest in January for Pr and in October for Tas ; it decreases from Spring, Autumn, Summer to Winter for Tas and from Summer, Spring, Autumn to Winter for Pr . Two parameters, i.e. the statistical significance level ( α ) and the minimum number of grids in every climate zone ( Nmin ), and their joint effects are significant for the effectiveness of FIGGRA ; normalization of a non-normal climate-variable distribution is helpful for the effectiveness only for Pr . For FIGGRA -based LSCCIAA studies, a low value of Nmin is recommended for both Pr and Tas , and a high and medium value of α for Pr and Tas , respectively.

Description: This paper describes a forward radiative transfer model and retrieval system (FMRS) for the Tropospheric Water and cloud ICE (TWICE) CubeSat instrument. We use the FMRS to simulate radiances for the TWICE's 14 millimeter- and submillimeter-wavelength channels for a tropical atmospheric state produced by a Weather Research and Forecasting (WRF) model simulation. We also perform simultaneous retrievals of cloud ice particle size, ice water content (IWC), water vapor content (H 2 O), and temperature from the simulated TWICE radiances using the FMRS. We show that the TWICE instrument is capable of retrieving ice particle size in the range of ~50-1000 μm in mass mean effective diameter with approximately 50% uncertainty. The uncertainties of other retrievals from TWICE are about 1 K for temperature, 50% for IWC and 20% for H 2 O.

Description: Accurate and real-time precipitation estimation is a challenging task for current and future space-borne measurements, which is essential to understand the global hydrological cycle. Recently, the Global Precipitation Measurement (GPM) satellites were launched as a next-generation rainfall mission for observing the global precipitation characteristics. The purpose of the GPM is to enhance the spatio-temporal resolution of global precipitation. The main objective of the present study is to assess the rainfall products from the GPM, especially the Integrated Multi-satellitE Retrievals for the GPM (IMERG) data by comparing with the ground-based observations. The multi temporal scale evaluations of rainfall involving sub-daily, diurnal, monthly, and seasonal scales were performed over the Indian subcontinent. The comparison shows that the IMERG performed better than the TRMM-3B42, although both rainfall products underestimated the observed rainfall compared to the ground-based measurements. The analyses also reveal that the TRMM-3B42 and IMERG data sets are able to represent the large-scale monsoon rainfall spatial features, but are having region-specific biases. The IMERG shows significant improvement in low rainfall estimates compared to the TRMM-3B42 for selected regions. In the spatial distribution, the IMERG shows higher rain rates compared to the TRMM-3B42, due to its enhanced spatial and temporal resolution. Apart from this, the characteristics of raindrop size distribution (DSD) obtained from the GPM mission dual-frequency precipitation radar (DPR) is assessed over the complex mountain terrain site in the Western Ghats, India using the DSD measured by a Joss-Waldvogel disdrometer.