ALBERT

Description: In this manuscript, the authors show how the Global Navigation Satellite Systems, GNSS (exemplified in the Global Positioning System, GPS), can be efficiently used for a very different purpose from that for which it was designed; as an accurate Solar observational tool, already operational from the open global GPS measurements available in real-time, and with some advantages regarding dedicated instruments onboard spacecraft. The very high correlation of the solar Extreme Ultraviolet (EUV) photon flux rate in the 26-34 mm spectral band, obtained from the SEM instrument onboard the SOHO spacecraft during Solar flares, is shown with the GNSS Solar Flare Activity Indicator (GSFLAI). The GSFLAI is defined as the gradient of the ionospheric vertical total electron content (VTEC) rate versus the cosine of the Solar zenith angle in the day hemisphere (which filters out non-Solar over-ionization), and it is measured from data collected by a global network of dual frequency GPS receivers (giving in this way continuous coverage). GSFLAI for 60 X class flares, 320 M class flares and 300 C class flares, occurred since 2001, were directly compared with the EUV Solar flux rate data to show existing correlations. It was found that the GSFLAI and EUV flux rate present the same linear relationship for all classes of flares, not only the strong and medium intensity ones, X and M-class, as in previous works, but also for the weakest C-class Solar flares, which is a remarkable result.

Description: Carbon dioxide ice is abundant on the Martian surface, and plays an important role in the planet's energy budget due to its high reflectivity and seasonal variation. Here, we adapt the terrestrial Snow, Ice, and Aerosol Radiation (SNICAR) model to simulate CO 2 snow albedo across the ultraviolet, visible, and near-IR spectrum (0.2-5.0 µm). We apply recent laboratory derived refractive indices of CO 2 ice, which produce higher broadband CO 2 snow albedo (0.93–0.98) than previously estimated. Compared with H 2 O snow, we find that CO 2 snow albedo is much higher in the near-IR spectrum, less dependent on ice grain size, less dependent on solar zenith angle, and more susceptible to darkening from dust. A mass concentration of 0.01% Martian dust reduces visible and near-IR CO 2 snow albedos by about 60% and 35%, respectively. The presence of small amounts of H 2 O snow on top of CO 2 snow can substantially decrease the surface albedo. Whereas 2.5 cm of H 2 O snow can completely mask the impact of underlying CO 2 ice or the surface, roughly twice as much overlying CO 2 snow is required to mask underlying H 2 O snow. Similarly, a 10% mixing ratio of H 2 O ice embedded in CO 2 snow decreases broadband albedo by 0.18, while 10% CO 2 ice elevates H 2 O snow broadband albedo by 0.10. We also present comparisons between hemispherical albedo produced by SNICAR and observations of directional reflectance of Martian polar ice caps. While imperfect, this best-fit analysis provides general ranges of physical parameters in different Martian environments that produce reasonable model–observation agreement.

Description: We assess the impact of transport of pollution from midlatitudes on the abundance of ozone in the Arctic in summer 2006 using the GEOS-Chem global chemical transport model and its adjoint. We find that although the impact of midlatitude emissions on ozone abundances in the Arctic is at a maximum in fall and winter, in July transport from North America, Asia, and Europe together contributed about 25% of surface ozone abundances in the Arctic. Throughout the summer, the dominant source of ozone in the Arctic troposphere was photochemical production within the Arctic, which accounted for more than 50% of the ozone in the Arctic boundary layer and as much as 30%–40% of the ozone in the middle troposphere. An adjoint sensitivity analysis of the impact of NOx emissions on ozone at Alert shows that on synoptic time scales in both the lower and middle troposphere, ozone abundances are more sensitive to emissions between 50°N and 70°N, with important influences from anthropogenic, biomass burning, soil, and lightning sources. Although local surface NOx emissions contribute to ozone formation, transport of NOx in the form of peroxyacetyl nitrate (PAN) from outside the Arctic and from the upper troposphere also contributed to ozone production in the lower troposphere. We find that in late May and June the release of NOx from PAN decomposition accounted for 93% and 55% of ozone production at the Arctic surface, respectively.

Description: The Indian subcontinent comprises of geological terranes of varied age and structural character. In this study, we provide new constraints to existing crustal models by inverting the P-to-s receiver functions (RFs) at 317 broadband seismic stations. Inversion results fill crucial gaps in existing velocity models (CRUST1.0 and SEAPS) by capturing regions which are less represented. The final model produced is much more heterogeneous and is able to capture the structural variations between closely spaced seismic stations. In comparison to the global models, major differences are seen for seismic stations located over various rift zones (e.g. Godavari, Narmada and Cambay) and those close to the coastal regions where transition from oceanic to continental crust is expected to create drastic changes in the crustal configuration. Seismic images are produced along various profiles using 49682 individual RFs recorded at 442 seismic stations. Lateral variations captured using migrated images across the Himalayan collisional front revealed the hitherto elusive southern extent of the Moho and intracrustal features south of the Main Central Thrust (MCT). Poisson's ratio and crustal thickness estimates obtained using H- k stacking technique and inversion of RFs are grossly similar lending credence to the robustness of inversions. An updated crustal thickness map produced using 1525 individual data points from controlled source seismics and RFs reveals a a) thickened crust (〉55 km) at the boundary of Dharwar Craton and Southern Granulite Terrain b) clear difference in crustal thickness estimates between Eastern Dharwar Craton and Western Dharwar Craton c) thinner crust beneath Cambay Basin between southwest Deccan Volcanic Province and Delhi Aravalli Fold Belt d) thinner crust (〈35 km) beneath Bengal Basin e) thicker crust (〉40 km) beneath paleo-rift zones like Narmada Son Lineament and Godavari Graben f) very thick crust beneath central Tibet (〉 65 km) with maximum lateral variations along the Himalayan collision front.

Description: Abstract The added value of biochar when applied along with fertilizers, beyond that of the fertilizers themselves, has not been summarized. Focusing on direct comparisons between biochar additions (≤ 20 t ha‐1) – separately considering the addition or not of inorganic fertilizers (IF) and/or organic amendments (OA) along with biochar – and two different controls (with and without the addition of IF and/or OA), we carried out a meta‐analysis to explain short‐term (1‐year) field responses in crop yield across different climates, soils, biochars, and management practices worldwide. Compared with the non‐fertilized control, a 26% (CI:15‐40%) increase in yield was observed with the use of IF only, whereas that of biochar along with IF caused a 48% (CI:30‐70%) increase. Compared to the use of IF only, the addition of biochar along with IF caused a 15% (CI:11‐19%) increase in yield, indicating that biochar was as effective as fertilizers in increasing crop yields when added in combination. The use of biochar alone did not increase crop yield regardless of the control considered. Whereas in the short‐term liming may have partly contributed to the beneficial effect of biochar (〉90% was plant‐derived) when added along with IF, a separate meta‐analysis – using those studies that reported crop yields for different years after a single biochar application – showed a 31% (CI:17‐49%) increase in crop yield observed over time (≥ 3 years), which denotes the influence of biochar properties other than liming (i.e., an increase in CEC). Our results also suggest that biochar application rates 〉 10 t ha‐1 do not contribute to greater crop yield (at least in the short term). Data limitations precluded identification of the influence of feedstock, production conditions, or climatic conditions without bias. As the response of crop yield to biochar addition was less a result of climatic zones or soil type than fertilizer use (chiefly N additions), the choice of nutrient addition along with biochar should be priorities for future research and development regardless of the region.

Description: The current version of Laboratoire de Météorologie Dynamique (LMD) Mars GCM (original-MGCM) uses annually repeating (prescribed) CO 2 snow albedo values based on the Thermal Emission Spectrometer observations. We integrate the Snow, Ice, and Aerosol Radiation (SNICAR) model with MGCM (SNICAR-MGCM) to prognostically determine H 2 O and CO 2 snow albedos interactively in the model. Using the new diagnostic capabilities of this model, we find that cryospheric surfaces (with dust) increase the global surface albedo of Mars by 0.022. Over snow-covered regions, SNICAR-MGCM simulates mean albedo that is higher by about 0.034 than prescribed values in original-MGCM. Globally, shortwave flux into the surface decreases by 1.26 W/m 2 , and net CO 2 snow deposition increases by about 4% with SNICAR-MGCM over one Martian annual cycle as compared to original-MGCM simulations. SNICAR integration reduces the mean global surface temperature, and the surface pressure of Mars by about 0.87% and 2.5% respectively. Changes in albedo also show a similar distribution to dust deposition over the globe. The SNICAR-MGCM model generates albedos with higher sensitivity to surface dust content as compared to original-MGCM. For snow-covered regions, we improve the correlation between albedo and optical depth of dust from -0.91 to -0.97 with SNICAR-MGCM as compared to the original-MGCM. Dust substantially darkens Mars' cryosphere, thereby reducing its impact on the global shortwave energy budget by more than half, relative to the impact of pure snow.