Sensitivity of land surface parameterization on Regional Spectral Model forecasts

Experiments were carried out to study the impact of different land surface schemes on a Regional Spectral Model (RSM) forecasts. RSM is based on the perturbation method of NCEP, where the dependent variables are the differences between the regional and global model fields called 'perturbations'. The perturbation method ensures the use of global model values as the base fields all over the domain and predicts the mesoscale features embedded in the base field forecasts. The first version of RSM has a land surface scheme with a single layer of soil moisture, which is the same as the operational global model with which it is nested. The second version of RSM has a land surface scheme with two layers of soil moisture and a more complex treatment of evaporation. The model was integrated for five days nested with the operational global spectral model during August 2001. The RSM with 2-layer soil moisture scheme was found to have slightly less easterly bias over north India. However, the two-layer scheme showed higher evaporation and precipitation over Andhra Pradesh region. Additionally, major differences were also observed in all the components of the surface energy balance over the same region

Comparative study of different orographic representations with respect to the Indian summer monsoon simulation

In spectral General Circulation Models that are now widely used in operational weather forecasting and research, the time dependent atmospheric parameters and orography are represented in the form of double series. In such spectral transform methods, Gibbs oscillations appear due to sharp gradients in terrain height, moisture, and cloud fields. The present paper shows the usefulness of different digital filters in reducing the negative values of orography. The application of filters also reduces the heights of the mountain peaks. This affects the Indian region the most, because of the presence of the Himalayas and the Western Ghats. In this paper, an attempt has been made to represent the orography by a new method, called the Filtered Modified Orography (FMO), in which a two dimensional Lanczos filter has been applied in the spectral domain globally with a subsequent local enhancement of the Himalayas and the Western Ghats. The dual advantages of reduction in negative orography values and enhancement of mountain peaks were achieved. A comparison with the envelope orography, where the mean orography is enhanced globally, shows that the new method is able to reduce some of the errors and disparities associated with the envelope technique while retaining some of the advantages of the barrier effect regionally. Results show reasonably good representation of global winds, geopotential and rainfall in FMO representation in T80 model of the National Centre for Medium Range Weather Forecasting

Skills of different mesoscale models over Indian region during monsoon season: Forecast errors

Performance of four mesoscale models namely, the MM5, ETA, RSM and WRF, run at NCMRWF for short range weather forecasting has been examined during monsoon-2006. Evaluation is carried out based upon comparisons between observations and day-1 and day-3 forecasts of wind, temperature, speci.c humidity, geopotential height, rainfall, systematic errors, root mean square errors and specific events like the monsoon depressions. It is very difficult to address the question of which model performs best over the Indian region? An honest answer is 'none'. Perhaps an ensemble approach would be the best. However, if we must make a final verdict, it can be stated that in general, (i) the WRF is able to produce best All India rainfall prediction compared to observations in the day-1 forecast and, the MM5 is able to produce best All India rainfall forecasts in day-3, but ETA and RSM are able to depict the best distribution of rainfall maxima along the west coast of India, (ii) the MM5 is able to produce least RMSE of wind and geopotential fields at most of the time, and (iii) the RSM is able to produce least errors in the day-1 forecasts of the tracks, while the ETA model produces least errors in the day-3 forecasts

Gendered forces at work: tentacular encounters from the nursery

Engaging with a feminist relational onto-epistemology, my research seeks to produce generative re-imaginings of how a gendered workforce comes to matter in a North London Montessori nursery. Debates, policies and practices around gender in the early years workforce continue to be firmly rooted in binary male/female framings (DfE, 2017), in which the recruitment of men in some ways has problematically taken centre stage through “recuperative masculinity” interventions (Lingard & Douglas, 1999). While these issues are not separate from Montessori early childhood contexts, the gender-neutral framing of Montessori works to let gender completely fall off the agenda. By employing feminist theorisations that foreground materiality, affect, discourse, place and temporalities, this study unsettles such presumed neutrality, and demonstrates ways a “gendered workforce” can be understood differently. The research emerged as situated evocations (Strathern, 1991) in a Montessori nursery in North London. Committed to Haraway’s (1988) situated knowledges and embodied perspectives, entangled authorship and “subjectivities” are emphasised as always already more-than-human. This is specifically made explicit in this thesis by how postcolonial and Dalit “subjectivities” intra-act to generate new theoretical connections, tensions and contradictions. Theoretical heterogeneity is thus welcomed by putting feminist “new” materialisms in conversation with anticolonial, decolonial and Dalit feminisms. These theoretical explorations have shaped the directions and orientations of this research. By paying attention to everyday “objects” in the nursery such as tea, cameras and snot, Haraway’s (2016) SF practice is mobilised to make visible the complex intra-actions of manifold forces that are at once composed of gendered and more-than-gendered (i.e. racialised, “classed” and “casted”) relations, stories and worlds that would otherwise be lost through methodological individualism and human exceptionalism. The more-than-human orientation in this research allows for a reconceptualisation of a “gendered workforce” as gendered forces that work on, across and through bodies (human and not), spaces, places, and scales of time. The reconceptualisation grants the possibility to attune to the multiple, in/determinate and contradictory materialisations of gendered and more-than-gendered forces that cut through onto-epistemic boundaries. Each encounter is constituted and reconstituted by masculinist forces that privilege narrow gender formations that determine what counts as “human” (Wynter 2003), and at once composed of minor gestures (Manning, 2016) that present generative potentialities for the innumerable possibilities for becominggendered Otherwise (Huuki & Renold, 2015) amid the recuperative masculinity drives of neoliberal capitalism. An approach that foregrounds a more-than-human and relational conception of gender makes a hopeful, generative and expansive contribution to the field

Altered Chromatin Occupancy of Master Regulators Underlies Evolutionary Divergence in the Transcriptional Landscape of Erythroid Differentiation

Erythropoiesis is one of the best understood examples of cellular differentiation. Morphologically, erythroid differentiation proceeds in a nearly identical fashion between humans and mice, but recent evidence has shown that networks of gene expression governing this process are divergent between species. We undertook a systematic comparative analysis of six histone modifications and four transcriptional master regulators in primary proerythroblasts and erythroid cell lines to better understand the underlying basis of these transcriptional differences. Our analyses suggest that while chromatin structure across orthologous promoters is strongly conserved, subtle differences are associated with transcriptional divergence between species. Many transcription factor (TF) occupancy sites were poorly conserved across species (∼25% for GATA1, TAL1, and NFE2) but were more conserved between proerythroblasts and cell lines derived from the same species. We found that certain cis-regulatory modules co-occupied by GATA1, TAL1, and KLF1 are under strict evolutionary constraint and localize to genes necessary for erythroid cell identity. More generally, we show that conserved TF occupancy sites are indicative of active regulatory regions and strong gene expression that is sustained during maturation. Our results suggest that evolutionary turnover of TF binding sites associates with changes in the underlying chromatin structure, driving transcriptional divergence. We provide examples of how this framework can be applied to understand epigenomic variation in specific regulatory regions, such as the β-globin gene locus. Our findings have important implications for understanding epigenomic changes that mediate variation in cellular differentiation across species, while also providing a valuable resource for studies of hematopoiesis

Johnson-Kendall-Roberts theory applied to living cells

Johnson-Kendall-Roberts (JKR) theory is an accurate model for strong adhesion energies of soft slightly deformable material. Little is known about the validity of this theory on complex systems such as living cells. We have addressed this problem using a depletion controlled cell adhesion and measured the force necessary to separate the cells with a micropipette technique. We show that the cytoskeleton can provide the cells with a 3D structure that is sufficiently elastic and has a sufficiently low deformability for JKR theory to be valid. When the cytoskeleton is disrupted, JKR theory is no longer applicable

Boreal summer sub-seasonal variability of the South Asian monsoon in the Met Office GloSea5 initialized coupled model

Boreal summer sub-seasonal variability in the Asian monsoon, otherwise known as the monsoon intra-seasonal oscillation (MISO), is one of the dominant modes of intraseasonal variability in the tropics, with large impacts on total monsoon rainfall and India’s agricultural production. However, our understanding of the mechanisms involved in MISO is incomplete and its simulation in various numerical models is often flawed. In this study, we focus on the objective evaluation of the fidelity of MISO simulation in the Met Office Global Seasonal forecast system version 5 (GloSea5), an initialized coupled model. We analyze a series of nine-member hindcasts from GloSea5 over 1996-2009 during the peak monsoon period (July-August) over the South-Asian monsoon domain focusing on aspects of the time-mean background state and air-sea interaction processes pertinent to MISO. Dominant modes during this period are evident in power spectrum analysis, but propagation and evolution characteristics of the MISO are not realistic. We find that simulated air-sea interactions in the central Indian Ocean are not supportive of MISO initiation in that region, likely a result of the low surface wind variance there. As a consequence, the expected near-quadrature phase relationship between SST and convection is not represented properly over the central equatorial Indian Ocean, and northward propagation from the equator is poorly simulated. This may reinforce the equatorial rainfall mean state bias in GloSea5

Selection of longitudinal modes in a terahertz quantum cascade laser via narrow-band injection seeding

A terahertz quantum cascade laser is injection seeded with narrow-band seed pulses generated from a periodically poled lithium niobate crystal. The spectral emission of the quantum cascade laser is controlled by the seed spectra

Investigation of time-resolved gain dynamics in an injection seeded terahertz quantum cascade laser

The evolution of the gain of terahertz quantum cascade laser during injection seeding is probed as a function of time. Oscillations of the gain are commensurate with the variations of the field envelope