Methane and carbon dioxide fluxes and their regional scalability for the European Arctic wetlands during the MAMM project in summer 2012

Airborne and ground-based measurements of methane (CH4), carbon dioxide (CO2) and boundary layer thermodynamics were recorded over the Fennoscandian landscape (67–69.5° N, 20–28° E) in July 2012 as part of the MAMM (Methane and other greenhouse gases in the Arctic: Measurements, process studies and Modelling) field campaign. Employing these airborne measurements and a simple boundary layer box model, net regional-scale (~ 100 km) fluxes were calculated to be 1.2 ± 0.5 mg CH4 h−1 m−2 and −350 ± 143 mg CO2 h−1 m−2. These airborne fluxes were found to be relatively consistent with seasonally averaged surface chamber (1.3 ± 1.0 mg CH4 h−1 m−2) and eddy covariance (1.3 ± 0.3 mg CH4 h−1 m−2 and −309 ± 306 mg CO2 h−1 m−2) flux measurements in the local area. The internal consistency of the aircraft-derived fluxes across a wide swath of Fennoscandia coupled with an excellent statistical comparison with local seasonally averaged ground-based measurements demonstrates the potential scalability of such localised measurements to regional-scale representativeness. Comparisons were also made to longer-term regional CH4 climatologies from the JULES (Joint UK Land Environment Simulator) and HYBRID8 land surface models within the area of the MAMM campaign. The average hourly emission flux output for the summer period (July–August) for the year 2012 was 0.084 mg CH4 h−1 m−2 (minimum 0.0 and maximum 0.21 mg CH4 h−1 m−2) for the JULES model and 0.088 mg CH4 h−1 m−2 (minimum 0.0008 and maximum 1.53 mg CH4 h−1 m−2) for HYBRID8. Based on these observations both models were found to significantly underestimate the CH4 emission flux in this region, which was linked to the under-prediction of the wetland extents generated by the models

Static charging of aircraft by collisions with ice crystals

Laboratory experiments measuring the charge transferred when ice crystals collide with various metal targets have shown that the primary influence on the magnitude and sign of the charging is the work function of the metal. The magnitude of the charging of two alloys used for aircraft manufacture varied by a factor of two. Further experiments are needed to characterise the charging of composite materials

On differentiating ground clutter and insect echoes from Doppler weather radars using archived data

Normally wind measurements from Doppler radars rely on the presence of rain. During fine weather, insects become a potential radar target for wind measurement. However, it is difficult to separate ground clutter and insect echoes when spectral or polarimetric methods are not available. Archived reflectivity and velocity data from repeated scans provide alternative methods. The probability of detection (POD) method, which maps areas with a persistent signal as ground clutter, is ineffective when most scans also contain persistent insect echoes. We developed a clutter detection method which maps the standard deviation of velocity (SDV) over a large number of scans, and can differentiate insects and ground clutter close to the radar. Beyond the range of persistent insect echoes, the POD method more thoroughly removes ground clutter. A new, pseudo-probability clutter map was created by combining the POD and SDV maps. The new map optimised ground clutter detection without removing insect echoes

Cloud liquid water and ice content retrieval by multiwavelength radar

Cloud liquid water and ice content retrieval in precipitating clouds by the differential attenuation method using a dual-wavelength radar, as a function of the wavelength pair, is first discussed. In the presence of non-Rayleigh scatterers, drizzle, or large ice crystals, an ambiguity appears between attenuation and non-Rayleigh scattering. The liquid water estimate is thus biased regardless of which pair is used. A new method using three wavelengths (long λl, medium λm, and short λs) is then proposed in order to overcome this ambiguity. Two dual-wavelength pairs, (λl, λm) and (λl, λs), are considered. With the (λl, λm) pair, ignoring the attenuation, a first estimate of the scattering term is computed. This scattering term is used with the (λl, λs) pair to obtain an estimate of the attenuation term. With the attenuation term and the (λl, λm) pair, a new estimate of the scattering term is computed, and so on until obtaining a stable result. The behavior of this method is analyzed through a numerical simulation and the processing of field data from 3-, 35-, and 94-GHz radars

Bibliography on hydrological applications of weather radar in the United Kingdom. Eighth edition (publications notified up to December 2011)

This bibliography of UK publications in the field of hydrological applications of weather radar is an update of the one produced in 2009. It has been compiled by the Inter-Agency Committee on the Hydrological Use of Weather Radar, with the help of the NERC Centre for Ecology & Hydrology at Wallingford. The Committee was originally established to provide a forum to foster links between organisations and individuals with expertise in the use of weather radar for hydrological purposes, in particular the users and the research community, and promote additional research and international contacts. The Committee's terms of reference and membership information can be found in Appendices to this document. This 8th edition includes papers from the International Symposium on “Weather Radar and Hydrology” (www.wrah2011.org), published as an IAHS Red Book conference proceedings (IAHS Publ. 351, iahs.info/redbooks/351.htm)

Inter-Agency Committee on the Hydrological Use of Weather Radar. Eighth report 2010 to 2012

As with the previous session report, we open reflecting on a period of significant UK flooding. The Summer and Autumn 2012 floods are still very fresh in the memory of those who have been trying to manage and respond to these events and for some the impacts are still affecting daily lives. Initial estimates indicate that the 2012 summer floods affected 2,700 properties with 70,000 properties receiving flood warnings. No doubt these damages estimates will increase as further information is gathered. However, what has changed from the previous 2007 to 2010 session has been the further development of meteorological and hydrological forecasting approaches and the emergence of hydrometeorology capabilities across England, Wales and Scotland to help improve prediction of these types of events. Radar continues to play an important role in flood risk and water management and the application of emerging science is the focus of this report. At the beginning of this current session, the Committee were keen to promote ways to influence the greater use of weather radar by operating agencies and to highlight areas of improvement and research in support of the user community. Specifically, the Committee wanted to explore various service and system developments, understand various ongoing research areas and their application for hydrology and water management, and promote the role of radar in flood risk management. Section 3 of the Committee report highlights research needs and presents the considerable range of ongoing science developments across various research groups. The approaches to raingauge-radar merging and data assimilation of radar data for Numerical Weather Prediction are presented as are the requirements from an established hydrological and emerging water management community. The requirement to provide forecasting capabilities for the whole of the country and for longer lead times was driven as an outcome of the Pitt Review. In Section 4, the efforts of some agencies in developing these capabilities are presented with emphasis on the development of countrywide grid-based hydrological models. In addition, Section 4 reflects on the largest upgrade to the UK radar network in its 30 year history and the introduction of significant radar capabilities that will benefit the user community once completed. Section 5 presents what has been the main focal point for the Committee’s attention during the session period. Following the Committee’s successful bid to host the International Symposium on Weather Radar and Hydrology, most of the Committee have been in some way involved in the successful delivery of this major event. Held over four days at the University of Exeter, this was the 8th in the symposium series and attracted over 250 international delegates. It is worth highlighting that following the organisation of Weather Radar and Hydrology 2011, the International Association of Hydrological Sciences has now published the conference proceedings as part of their Red Book series. The volume brings together over 100 peer-reviewed papers from the symposium providing a valuable record of the current activity in this field. Finally, the appendices to this session report provide an overview of the UK academic and operational agency activity in this sector