ESTIMATION OF THE URBAN HEAT ISLAND IN LOCAL CLIMATE CHANGE AND VULNERABILITY ASSESSMENT FOR AIR QUALITY IN DELHI

Delhi experience the effect of high heat compared to the rural surroundings during hot seasons. This phenomenon is known as Urban Heat Island (UHI) which exerts a significant influence on local climate. Urban climate, land cover, land use, vegetation ratio and surface temperature have been cited as the main contributors to the UHI effect. This paper focuses on urban heat islands (UHI) as a specific problem expected to be exacerbated by local climate change. A simple formula has been used to calculate the urban heat island (UHI) from a set of land surface temperature data for observed temperatures by Landsat 7 and 8 and quantifies how this urban heat island effect on local climate change response strategy 2000- 2014. The aim is to identify climate sensitive urban patterns during summer, winter and monsoon months. The study reveals that the intensity of heat island varies from 3 C° to 8 C° and intensity is high during summer season compared to monsoon and winter seasons. In Delhi the formation of heat island is controlled by vegetation density. It has been found that UHI become bigger during cooling at night time. The urban heat island helps to decrease air quality during summer. UHI coupled with high land surface temperature conditions during summer season causes human discomfort and higher death rates in Delhi. These changes reflect sensitivity to variations in regional climate alone, so omit other factors such as changes in land use, emissions, land surface temperature, or synergies on size and shape of heat islands

Frequency modulated few-cycle optical pulse trains induced controllable ultrafast coherent population oscillations in three-level atomic systems

We report a study on the ultrafast coherent population oscillations (UCPO) in two level atoms induced by the frequency modulated few-cycle optical pulse train. The phenomenon of UCPO is investigated by numerically solving the optical Bloch equations beyond the rotating wave approximation. We demonstrate that the quantum state of the atoms and the frequency of UCPO may be controlled by controlling the number of pulses in the pulse trains and the pulse repetition time respectively. Moreover, the robustness of the population inversion against the variation of the laser pulse parameters is also investigated. The proposed scheme may be useful for the creation of atoms in selected quantum state for desired time duration and may have potential applications in ultrafast optical switching

Optical dipole force on ladder-like three-level atomic systems driven by chirped few-cycle-pulse laser fields

We report a study on the optical dipole force in a ladder like three level atomic systems in the context of coherent population transfer with the chirped few-cycle-pulse laser fields. The phenomenon of coherent population transfer is investigated by numerically solving the appropriate density matrix equations beyond the rotating wave approximation. On the other hand, optical dipole force is calculated by numerically solving the force equation and density matrix equations self-consistently. By analysing the centre-of-mass motion, it is shown that the optical dipole force with chirped pulses may be used for focusing and defocusing of atoms in an atomic beam similar to the near or non-resonant optical dipole force. Moreover, the robustness of the population transfer against the variation of the pulse parameters and the effect of the variation of the Rabi frequencies and the chirp rates on the optical dipole force are also investigated. The proposed scheme may open new perspectives in the focusing and de-focusing of atoms and molecules in an atomic beam, since this scheme mitigates the demand for the generation of transform-limited pulse laser fields at arbitrary frequencies

Glacio-archaeological evidence of permanent settlements within a glacier end moraine complex during 980-1840 AD: The Miyar Basin, Lahaul Himalaya, India

This study presents glacio-archaeological evidence from the Miyar basin, Lahaul Himalaya, that points towards the former presence of a well settled agricultural society, within a glacier end moraine complex. Three high altitude villages (Tharang, Phundang and Patam, now in ruins) with elaborate irrigation networks thrived within the end moraine complex of Tharang glacier at 3700 m a.s.l. Evidence exists in the form of dilapidated houses which had an organised internal space, chronologically constrained by radiocarbon (14C) dating. These settlements occupied the end moraine complex between 980 and 1840 CE, thereby encompassing the majority of Little Ice Age period (1300–1600 CE), as defined elsewhere. The existence of settlements along with an irrigation system and associate fields at ∼3700-3800 m a.s.l. for almost ∼860 years during the late 10th to early 19th centuries suggests more favourable climatic (warm) conditions that at present. By contrast, present habitation is restricted to areas below ∼3500 m a.s.l. However, the slope controlled irrigation system also suggests moisture stressed conditions during the 980–1840 CE period, similar to present. The available temperature and snowfall proxies for the region support our proposed timing, and suggest favourable climatic conditions for the survival of these settlements

Coherent population trapping in negatively charged self-assembled quantum dots using a train of femtosecond pulses

We demonstrate the coherent population trapping in a single quantum dot and an ensemble of negatively charged quantum dots using a train of femtosecond pulses. Particularly in an ensemble of quantum dots, we show that the detrimental effects due to the inhomogeneous distribution of their properties can be minimized by appropriately choosing the pulse-train parameters and the magnetic-field strength in such a way that the electron-Zeeman splitting is an integer multiple of the pulse repetition rate