Ventilation effects on humidity measurements in thermometer screens

Relative humidity (RH) measurements, as derived from wet-bulb and dry-bulb thermometers operated as a psychrometer within a thermometer screen, have limited accuracy because of natural ventilation variations. Standard RH calculations generally assume a fixed screen psychrometer coefficient, but this is too small during poor ventilation. By comparing a reference humidity probe—exposed within a screen containing a psychrometer—with wind-speed measurements under controlled conditions, a wind-speed correction for the screen psychrometer coefficient has been derived and applicable when 2-metre wind speeds fall below 3 ms–1. Applying this to hourly-averaged data reduced the mean moist RH bias of the psychrometer (over the reference probe) from 1.2% to 0.4%, and reduced the inter-quartile range of the RH differences from 2.0% to 0.8%. This correction is particularly amenable to automatic measurement systems

Data sources for rescuing the rich heritage of Mediterranean historical surface climate data

10.1002/gdj3.4Availability of long-term and high-quality instrumental climate records is still insufficient and the rich heritage of meteorological surface observations is largely underexploited in many parts of the world. This is particularly striking over the Greater Mediterranean region (GMR), where meteorological observations have been taken since the 18th century at some locations. The lack of high quality and long series here is despite this region being regarded as a climate change hot spot. This article mainly assesses relevant sources containing Mediterranean historical climate data and metadata either from online repositories worldwide or physical archives, with the emphasis here on the rich holdings kept at French archives. A particular case study is the data rescue (DARE) program undertaken by the Algerian National Meteorological Service, as well as some of the past and ongoing projects and initiatives aimed at enhancing climate data availability and accessibility over the GMR. Our findings point to the high potential for undertaking DARE activities over the GMR and the need for bringing longer and higher quality climate time series to support a diverse number of scientific and technical assessments and policies

From urban meteorology, climate and environment research to integrated city services

Accelerating growth of urban populations, especially in developing countries, has become a driving force of human development. Crowded cities are centres of creativity and economic progress, but polluted air, flooding and other climate impacts, means they also face major weather, climate and environment-related challenges. Increasingly dense, complex and interdependent urban systems leave cities vulnerable: a single extreme event can lead to a widespread breakdown of a city’s infrastructure often through domino effects. The World Meteorological Organization (WMO) recognizes that rapid urbanization necessitates new types of services which make the best use of science and technology and considers the challenge of delivering these as one of the main priorities for the meteorological community. Such Integrated Urban Weather, Environment and Climate Services should assist cities in facing hazards such as storm surges, flooding, heat waves, and air pollution episodes, especially in changing climates. The aim is to build urban services that meet the special needs of cities through a combination of dense observation networks, high-resolution forecasts, multi-hazard early warning systems, and climate services for reducing emissions, that will enable the building of resilient, thriving sustainable cities that promote the Sustainable Development Goals. A number of recent international studies have been initiated to explore these issues. The paper provides a brief overview of recent WMO and collaborators research programs and activities in urban hydrometeorology, climate and air pollution; describes the novel concept of urban integrated weather, climate and environment related services; and highlights research needs for their realisation

Developing a quick guide on presenting data and uncertainty

This paper describes the rationale, development and testing of a quick guide leaflet on the presentation of data and uncertainty. While tools for capturing, analysing and presenting data become more advanced, the fundamentals of presenting data with adequate context and clarity remain unchanged. The leaflet, aimed at scientists generating and presenting data, was created as part of an interdisciplinary collaboration (meteorologists, information designers, psychologists) working within the PURE Network project RACER, funded by the UK Natural Environment Research Council. A copy of the leaflet is included in this article

Preliminary report of the ICRISAT/WMO Symposium/Planning meeting

Agriculturists and climatologists from 18 countries joined ICRISAT scientists for wide-ranging discussions the past two weeks on how agroclimatology can be put to better use in improving the production of sorghum and millet. The planning meeting and international symposium on "The Agrometeorology sorghum and Millet in the Semi-Arid Tropics" were sponsored by ICRISAT and the World Meteorological Organization (WMO), and agency of the United Nations. Co-sponsors were the Food and Agricultural Organization of the UN(FAO), INTSORMIL, a program of international research on sorghum and millet sponsored by the U.S. Government, and Texas A&M University, USA. A total of 112 scientists participated in the sessions that began with a series of planning meeting 8 November and ended with a 5-day symposium 15-19 November. The meeting were held at ICRISAT Center, the headquarters and main research farm of the International Crops Research Institute for the Semi-Arid Tropics at Patancheru, near Hyderaba

Spike output and synaptic plasticity in a feed-forward inhibitory microcircuit in the cerebellar cortex

Feed-forward inhibitory circuits are common building blocks in the mammalian brain and lead to excitatory input also activating inhibitory input to a common postsynaptic neuron. Such circuits are important for regulating neuronal excitability and timing of activity in the brain. In this thesis I have explored the mechanisms and consequences of feed-forward inhibition in the rat cerebellar cortex, which is known to be involved in coordination and timing of movement. Voltage clamp recordings from Purkinje cells in cerebellar slices exhibit a biphasic current waveform in response to stimulation of parallel fibres, consisting of an excitatory postsynaptic current (EPSC) followed by an inhibitory postsynaptic current (IPSC). The latency difference between the two components - only 1.4 ms - and the complete block of the biphasic response by glutamate receptor antagonists confirmed the second component as feed forward inhibition (FFI). The rapid onset of FFI shortens EPSPs, which enhances spike precision and limits summation of independent inputs. Next, I showed that the latency of FFI does not change with distance along active parallel fibres. This suggests that desynchronisation of action potentials travelling along the parallel fibres is insufficient to cause feed-forward inhibition to arrive ahead of excitation, a theory previously used to explain the observed lack of 'beams' of active Purkinje cells along the parallel fibres. Instead, it is argued that this may result from spatial or temporal spread of activity in the granule cell layer leading to early arrival of inhibition. Both excitation and inhibition in Purkinje cells are subject to plastic changes induced by climbing fibre activation. In a feed-forward network, what is the net effect of this plasticity on the output of the cerebellar cortex First I showed that both inhibition and excitation undergo long-term depression (LTD) to a similar extent when paired with climbing fibre input. This plasticity was reflected in corresponding changes in Purkinje cell spike output triggered by independent inhibitory and excitatory inputs: parallel fibre LTD reduced, and LTD of inhibition increased the number of spikes evoked by the respective inputs. To examine the net effect of simultaneous plasticity of inhibition and excitation on Purkinje cell output with a feed-forward input, I simulated synaptic inputs with dynamic clamp and systematically changed the ratio of excitation and inhibition as well as the amplitude of both components. Depressing both components as observed when pairing the isolated components with the climbing fibre, reduced spike output for feed-forward inputs with small inhibitory components, while for inputs with stronger inhibition the spike output increased. Finally, I showed that pauses after spike bursts evoked by strong parallel fibre inputs in the absence of inhibition scaled with input strength. A classical climbing fibre LTD protocol reduced these pauses, which thus encode information stored by synaptic plasticity for downstream neurons. These findings are discussed in the context of classical theories of cerebellar learning, which are concluded to require revision or refinement

Five years of observations of ozone profiles over Lauder, New Zealand

Altitude profiles of ozone (O3) over Lauder (45°S, 170°E) performed using a lidar, ozonesondes, and the satellite-borne Stratospheric Aerosol and Gas Experiment (SAGE II) instrument are presented. These data form one of the few long-term sets of O3 profiles at a Southern Hemisphere location. In the 5 years of data presented, the dominant variation is the annual cycle, the phase and amplitude of which differ below and above 27.5 km. Superposed are irregular episodic variations, caused by various processes. The first process studied is stratosphere-troposphere exchange, characterized by dry and O3-rich air residing in the troposphere, which was found in 21% of the measurements. The second relates to the positioning of the higher polar vortex over Lauder, often in combination with the exchange of air between midlatitude and subtropical stratospheric regions. We present examples of this which were observed over Lauder during the 1997 winter. This winter was selected for further study because of the record-low O3 amounts measured. The third process is mixing of O3-depleted vortex air with midlatitude air after the vortex breakup. We present one example, which shows that a filament originating from the depleted Antarctic vortex significantly lowers O3 amounts over Lauder around 27 November 1997. There is thus a connection between Antarctic O3 depletion and later decrease of O3 amounts at a Southern Hemisphere midlatitude location, namely Lauder

Status of the Global Observing System for Climate

Status of the Global Observing System for Climat

Asperitas – a newly identified cloud supplementary feature

Cloud images obtained through a crowd-sourced international observing network suggest a cloud variety that has hitherto not been explicitly classified. This cloud feature shows a roughened base, which, under some solar illumination conditions, provides a particularly dramatic appearance. The growing body of photographic observations have led the World Meteorological Organisation to consider adding ‘asperitas’ to the 2017 edition of the International Cloud Atlas as a new form of supplementary cloud feature. We compare reported sightings with available meteorological data to investigate the conditions that give rise to this newly recognised cloud description