Variability of southwest monsoon rainfall over West Bengal

Monthly and seasonal variations of southwest monsoon rainfall over the districts of Gangetic and Sub-Himalayan West Bengal are presented and their differences discussed. Latitudinal variations of monsoon rainfall are brought out. Decadal means of seasonal rainfall over plains are compared with those at higher elevations and northern latitudes. An attempt is made to study long term rainfall trends.

The relation between the zonal jets and ammonia anomalies in Jupiter

<div> <div>Juno's six‐channel MWR measurements might reveal information about the structure of the wind profile below the cloud level. These measurements are used to calculate the nadir brightness temperature (T<sub>b</sub>), a profile determined by temperature and by the opacity of the atmosphere. This opacity for the relevant frequencies of the MWR is determined mostly by ammonia abundance. The T<sub>b</sub> vary considerably between the different channels (indicating on different depths) and between latitudes. Here, we take the <!-- mathfontold --> T<sub>b</sub> as an indicator for ammonia concentration and examine the relation to the zonal jets. We find that different theoretical mechanisms can explain this relation at different latitudes. At the equatorial region, the superrotation is accompanied by vertical upwelling. This vertical advection, driven by a convergence of eddy fluxes directed perpendicular to the axis of rotation, is shown to explain the equatorial ammonia enrichment. At the mid-latitudes, assuming that the ammonia is enriched with depth, alternating Ferrel-like cells framed by opposite vertical velocities redistributes the ammonia, maximizing its meridional gradient where the jet peaks. This hypothesis is well apparent in the data, using both correlation analysis and theoretical arguments. We find that dynamical reasoning, suggesting on vertical velocities through the cloud-level zonal jets, can explain the latitudinal variations in <!-- mathfontold --> T<sub>b,</sub> under the assumption that they are caused by ammonia abundance anomalies.</div> </div>

Tilt angle and lifetime of sunspot groups

We use the Catalog of Solar Activity (CSA) to study the latitudinal variations of tilt of solar active regions. The tilt angles β are computed taking into account changes of the heliographic grid with latitude ϕ. We show that when sunspot groups of different sizes and lifetimes are included, a classical representation of the Joy’s law as a linear function of latitude (β∝ϕ) is only the first approximation valid within a limited range of latitudes (−25○ ≤ ϕ ≤ +25○). Outside this range, the functional dependence β = f(ϕ) becomes non-linear. Separating the dataset on large long-living groups (LLG) and small short-living groups (SSG) reveals two quite different dependencies in β = f(ϕ): non-linearity in tilt is only present in LLGs and the steepness of linear section of β = f(ϕ) fit is higher for LLGs. This suggests a difference in the physical properties of two populations of solar groups, which could be hypothesized as an indication of different localization of subsurface zones of their formation in the framework of a distributed dynamo. However, since CSA contains the coordinates of sunspots averaged over the lifetime (or disk passage) of each group, one cannot ruled out that the difference in tilts of SSG and LLG groups may be affected by the evolution of tilt angles during the lifetime/disk passage of the groups.