We develop an experimental daily surface heat flux data set based on satellite observations to study subseasonal variability (periods shorter than 90 days) in the tropical Indian Ocean. We use incoming shortwave and longwave radiation from the International Satellite Cloud Climatology Project, and sea surface temperature (SST) from microwave sensors, to estimate net radiative flux. Latent and sensible heat fluxes are estimated from scatterometer winds and near‐surface air temperature and specific humidity from Atmospheric Infrared Sounder (AIRS) observations calibrated to buoy data. Seasonal biases in net heat flux are generally within 10 W m−2 of estimates from moorings, and the phases and amplitudes of subseasonal variability of heat fluxes are realistic. We find that the contribution of subseasonal changes in air‐sea humidity gradients to latent heat flux equals or exceeds the contribution of subseasonal changes in wind speed in all seasons. SST responds coherently to subseasonal oscillations of net heat flux associated with active and suppressed phases of atmospheric convection in the summer hemisphere. Thus, subseasonal SST changes are mainly forced by heat flux in the northeast Indian Ocean in northern summer, and in the 15°S–5°N latitude belt in southern summer. In the winter hemisphere, subseasonal SST changes are not a one‐dimensional response to heat flux, implying that they are mainly due to oceanic advection, entrainment, or vertical mixing. The coherent evolution of subseasonal SST variability and surface heat flux suggests active coupling between SST and large‐scale, organized tropical convection in the summer season.

Note: Please see pdf for full abstract with equations An adiabatic process is a thermodynamic process in which there is no exchange of heat energy or particles between the system and its surroundings. However the surroundings can alter the mechanical energy or potential energy of the system. This fact is not borne out well in any of the standard textbooks. Here we explicitly discuss the case where we alter the potential energy component and its consequences. There is a misconception that the reduced internal energy performs an external work during this process and that the net energy change of the system is zero. We are going to bust both these myths. Both the internal energy and stored mechanical energy either increase or decrease together in tandem depending on the external forcing. They do not feed each other in the absence of externally induced changes. The usual relationships we use, that is PVγ = Constant and P1-γTγ = Constant are valid only when the changes in external forcing is very minute. When the imposed external pressure is very small or very large compared to the system pressure then we get large errors in the calculations. Here we derive accurate equations which are valid over the entire range of operation. We also note that the textbook expressions can not satisfy both the energy eqn and ideal gas law simultaneously. Further the textbook eqns indicate that it must be a reversible process. But the accurate eqns show that this process is inherently irreversible.

In a Gas Cylinder - Piston system, when the gas raises a mass M (on the piston) from a lower level z to an upper level z', then we say the gas has performed some work, W = Mg(z'-z). We can utilise two kinds of thermodynamic actions to enhance the height of the piston, without altering the mass on the piston. (A) We can enhance the temperature of the gas. (B) We can increase the number of particles in the system. The first process (A) is a pure Isobaric process, here the Volume expansion is proportional to the increasing Temperature. Process (B) is a combination of Isobaric-Isothermal process, here the expansion is proportional to the addition (pumping in) of extra Gas Particles. The textbook description of an Heat (Carnot) Engine is completely wrong. It is described as composed of 4 steps, (i) Adiabatic compression → (ii) Isothermal expansion → (iii) Adiabatic expansion and → (iv) Isothermal compression. In this, steps (ii) and (iv) ought to be Isobaric as it is described as achieved by connecting the system to an heat bath (source/sink) with only heat transfer and no mass transfer. In order to realise an Isothermal process we need to pump in or pump out gas particles at the same temperature as the particles in the system. Besides in steps (i) and (iii) the formulae used to characterise the adiabatic process are also wrong. When we use the proper steps with correct eqns, the maximum possible efficiency turns out to be only 1/(1+f/2), where f = degrees of freedom of the gas particles. The efficieny is not 1-T0/T1, where T0 = sink temperature and T1 = source temperature, as is usually calculated from the wrong theory.

We analyse a simple one dimensional arrangement of identical springs coupled with identical masses to understand longitudinal oscillations on the spring-mass chain. D'Alembert wave eqn implies only one wave-speed value, there is no wave dispersion. Ab initio analysis of the normal modes suggests that wave-speed in a closed-chain has dispersion. In the open-chain case, we can realistically associate a wave-length and wave-speed only for about half the normal mode solutions, because the higher frequency half of the modes on open-chains do not have sinusoidal solutions. In the normal mode analysis we find sinusoidal variation of frequency wrt mode number, not linear as expected by the idea of harmonics. Framing of D'Alembert wave equation is untenable. It is purely a geometric construct without any Physics basis to it.

Note: Please see pdf for full abstract with equations An adiabatic process is described as a thermodynamic process where there is no exchange of heat or mass between the system and its surroundings. However there will be an exchange of mechanical work. In this article we specifically consider a class of adiabatic processes where the imposed external pressure remains constant until the system pressure comes in equilibrium with the imposed external pressure. We normally use the expression PVγ = Constant to describe such processes, but surprisingly it does not satisfy the 1st Law of Thermodynamics. If Pi, Pƒ are the initial and final state Pressure and Vi, Vƒ are the initial and final state Volume of gas in a cylinder, then the correct expression we get is Vƒ = Vi(1 + Pi/Pƒ ƒ/2) / (1 + ƒ/2), where ƒ = degree of freedom of the gas molecules. Also note, γ = (ƒ +2) / ƒ. We can also derive PiVγi = PƒVγƒ when Pƒ ≈ Pi in the correct expression. Another point we can note is this process is inherently irreversible.