The interaction of Indian monsoon depressions with northwesterly mid-level dry intrusions

Monsoon depressions (MDs) bring substantial monsoon rainfall to northern and central India. These events usually form over the Bay of Bengal and travel across northern India toward Pakistan. Using European Centre for Medium-Range Weather Forecasting Interim Reanalysis, an MD tracking algorithm, and an objective identification method, we find that about 40% of MDs interact with northerly intrusions of dry desert air masses as the MDs traverse the subcontinent. MD interactions with dry intrusions are often preceded by positive potential vorticity anomalies on the subtropical jet and low level anticyclonic anomalies over the north Arabian Sea. Dry intrusions nearly halve the precipitation rate in the southwest quadrant of MDs, where MDs rain the most. However, dry intrusions increase the rainfall rate near the MD center. Similarly, ascent is reduced west of the MD center and enhanced at the MD center, especially in the upper troposphere. The reduced ascent west of MD centers is likely attributable to changes in vertical shear reducing differential cyclonic vorticity advection. Dry intrusions slightly reduce MDs’ propagation speed. For the mid-upper level vortex, this can be explained by anomalous westerlies reducing propagation by adiabatic advection. For the lower tropospheric vortex, it is likely that reduced diabatic generation of PV plays a role in slowing propagation, along with reduced adiabatic advection

Looking under the hood: A comparison of techno-economic assumptions across national and global integrated assessment models

Integrated assessment models are extensively used in the analysis of climate change mitigation and are informing national decision makers as well as contribute to international scientific assessments. This paper conducts a comprehensive review of techno-economic assumptions in the electricity sector among fifteen different global and national integrated assessment models. Particular focus is given to six major economies in the world: Brazil, China, the EU, India, Japan and the US. The comparison reveals that techno-economic characteristics are quite different across integrated assessment models, both for the base year and future years. It is, however, important to recognize that techno-economic assessments from the literature exhibit an equally large range of parameters as the integrated assessment models reviewed. Beyond numerical differences, the representation of technologies also differs among models, which needs to be taken into account when comparing numerical parameters. While desirable, it seems difficult to fully harmonize techno-economic parameters across a broader range of models due to structural differences in the representation of technology. Therefore, making techno-economic parameters available in the future, together with of the technology representation as well as the exact definitions of the parameters should become the standard approach as it allows an open discussion of appropriate assumptions. © 2019 The Author

Taking stock of national climate policies to evaluate implementation of the Paris Agreement

Many countries have implemented national climate policies to accomplish pledged Nationally Determined Contributions and to contribute to the temperature objectives of the Paris Agreement on climate change. In 2023, the global stocktake will assess the combined effort of countries. Here, based on a public policy database and a multi-model scenario analysis, we show that implementation of current policies leaves a median emission gap of 22.4 to 28.2 GtCO2eq by 2030 with the optimal pathways to implement the well below 2 °C and 1.5 °C Paris goals. If Nationally Determined Contributions would be fully implemented, this gap would be reduced by a third. Interestingly, the countries evaluated were found to not achieve their pledged contributions with implemented policies (implementation gap), or to have an ambition gap with optimal pathways towards well below 2 °C. This shows that all countries would need to accelerate the implementation of policies for renewable technologies, while efficiency improvements are especially important in emerging countries and fossil-fuel-dependent countries

Taking stock of national climate policies to evaluate implementation of the Paris Agreement

Many countries have implemented national climate policies to accomplish pledged Nationally Determined Contributions and to contribute to the temperature objectives of the Paris Agreement on climate change. In 2023, the global stocktake will assess the combined effort of countries. Here, based on a public policy database and a multi-model scenario analysis, we show that implementation of current policies leaves a median emission gap of 22.4 to 28.2 GtCO2eq by 2030 with the optimal pathways to implement the well below 2 °C and 1.5 °C Paris goals. If Nationally Determined Contributions would be fully implemented, this gap would be reduced by a third. Interestingly, the countries evaluated were found to not achieve their pledged contributions with implemented policies (implementation gap), or to have an ambition gap with optimal pathways towards well below 2 °C. This shows that all countries would need to accelerate the implementation of policies for renewable technologies, while efficiency improvements are especially important in emerging countries and fossil-fuel-dependent countries

CFD simulation of an UAV across a microburst

Weather plays a vital role in the safe operation of aircraft and other flying vehicles. One of the least known and most significant weather phenomena is the wind shear which is defined as a small-scale meteorological phenomenon accompanied by rapidly changing winds over a small distance. One of the leading causes of wind shear includes severe weather systems like thunderstorms, downburst and many others. Of these, the straight-line winds from the outflow of localised downdrafts are believed to produce rapid changes of wind shear in small spatiotemporal scale and are called as microburst. Due to the highly restricted structure of winds and its dependence on various scales of motion, it becomes complicated for the numerical weather models to predict the evolution of such systems accurately. The primary focus of the thesis is to investigate the structure and flow-dynamics of an isolated stationary microburst using CFD simulations. The microburst-induced wind fields are modelled as a jet impingement technique on to a flat surface using both axisymmetric and planar mathematical formulation. Reynolds Averaged Navier Stokes (RANS) numerical model has been used in the present study. The simulated mean wind profile exhibits similar characteristics observed in a full-scale microburst. As per the steady state RANS model, the normalised peak radial velocity was found at a radial distance of nearly 100m above the ground. The results of the numerical simulation were compared with different laboratory experiments and other field events which match well with the numerical results with discrepancies of less than 5 % at few radial locations. In addition to this, high-resolution satellite data were also used to validate the simulation results. The numerical results compared favourably with the satellite observations suggesting the ability of CFD to aid in better understanding and modelling the flow features. The thesis also deals with the simulation on an airfoil in the turbulent wind field generated by the microburst to study its effects during take-off and landing operations. The transient loading effects on the UAV is also analysed with an increase in microburst outflow with an estimate on the peak loads and moments generated on the model.Master of Science (Aerospace Engineering

Regional characteristics of extreme precipitation events over Aotearoa New Zealand

We document 1394 extreme precipitation events (EPEs) over Aotearoa New Zealand’s (ANZ) Regional Councils between March 1996 and December 2021. The characteristics of EPEs are documented using a novel spatio-temporal framework that diagnoses the peak intensity, duration, and accumulation of the EPE using the ERA-5 and MERRA-2 reanalysis products. Properties of EPEs were evaluated according to region across ANZ, and clear regional differences are highlighted. In particular, it is found that the duration of an EPE has a stronger influence than the peak intensity on the total accumulated precipitation across all regions and precipitation event types (large-scale or convective). Since larger precipitation accumulations have greater potential to cause extensive flooding over larger areas, an important implication is the need for numerical weather prediction in ANZ to forecast the duration of an intense precipitation event adequately in order to improve emergency preparedness

Looking under the hood: A comparison of techno-economic assumptions across national and global integrated assessment models

Integrated assessment models are extensively used in the analysis of climate change mitigation and are informing national decision makers as well as contribute to international scientific assessments. This paper conducts a comprehensive review of techno-economic assumptions in the electricity sector among fifteen different global and national integrated assessment models. Particular focus is given to six major economies in the world: Brazil, China, the EU, India, Japan and the US. The comparison reveals that techno-economic characteristics are quite different across integrated assessment models, both for the base year and future years. It is, however, important to recognize that techno-economic assessments from the literature exhibit an equally large range of parameters as the integrated assessment models reviewed. Beyond numerical differences, the representation of technologies also differs among models, which needs to be taken into account when comparing numerical parameters. While desirable, it seems difficult to fully harmonize techno-economic parameters across a broader range of models due to structural differences in the representation of technology. Therefore, making techno-economic parameters available in the future, together with of the technology representation as well as the exact definitions of the parameters should become the standard approach as it allows an open discussion of appropriate assumptions.JRC.C.6-Economics of Climate Change, Energy and Transpor

Looking under the hood : A comparison of techno-economic assumptions across national and global integrated assessment models

Integrated assessment models are extensively used in the analysis of climate change mitigation and are informing national decision makers as well as contribute to international scientific assessments. This paper conducts a comprehensive review of techno-economic assumptions in the electricity sector among fifteen different global and national integrated assessment models. Particular focus is given to six major economies in the world: Brazil, China, the EU, India, Japan and the US. The comparison reveals that techno-economic characteristics are quite different across integrated assessment models, both for the base year and future years. It is, however, important to recognize that techno-economic assessments from the literature exhibit an equally large range of parameters as the integrated assessment models reviewed. Beyond numerical differences, the representation of technologies also differs among models, which needs to be taken into account when comparing numerical parameters. While desirable, it seems difficult to fully harmonize techno-economic parameters across a broader range of models due to structural differences in the representation of technology. Therefore, making techno-economic parameters available in the future, together with of the technology representation as well as the exact definitions of the parameters should become the standard approach as it allows an open discussion of appropriate assumptions