
Helen Claire WardUniversity of Innsbruck | UIBK · Institute of Atmospheric and Cryospheric Sciences
Helen Claire Ward
MPhys, PhD
About
64
Publications
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2,189
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Introduction
Additional affiliations
May 2017 - present
September 2016 - October 2016
April 2014 - May 2017
Education
October 2009 - March 2013
October 2005 - June 2009
Publications
Publications (64)
Urban surface albedo is an essential biophysical variable in the surface energy balance across all scales, from micro-scale (materials) to the globe, changing with land covers and three-dimensional structures over urban areas. Urban albedos are dynamic over space and time but have not yet been quantified over global scales due to the lack of high-r...
The process of coupling the Surface Urban Energy and Water Scheme (SUEWS) into the Weather Research and Forecasting (WRF) model is presented, including pre-processing of model parameters to represent spatial variability in surface characteristics. Fluxes and mixed-layer height observations in the southern UK are used to evaluate a 2-week period in...
The process of coupling the Surface Urban Energy and Water Scheme (SUEWS) into the Weather research and forecasting (WRF) model is presented, including pre-processing of model parameters to represent spatial variability of surface characteristics. Fluxes and mixed layer height observations in the southern UK are used to evaluate a two-week period i...
A total of 20 urban neighbourhood-scale eddy covariance flux tower datasets are made openly available after being harmonized to create a 50 site–year collection with broad diversity in climate and urban surface characteristics. Variables needed as inputs for land surface models (incoming radiation, temperature, humidity, air pressure, wind and prec...
Scintillometry is a non-invasive measurement technique for acquiring spatially-averaged surface heat and moisture fluxes in areas where setting up arrays of instruments can be expensive and logistically difficult. As a path-averaged measurement, scintillometry is a valuable tool for measuring integrated atmospheric turbulence over agricultural terr...
Twenty urban neighbourhood-scale eddy covariance flux tower datasets have been harmonized and quality controlled, producing a 50 site-year collection with broad diversity in climate and urban surface characteristics. Observations are gap-filled and prepended with 10 years of reanalysis-derived local data to enable use as spin up and forcing for lan...
This study represents the first detailed analysis of multi-year, near-surface turbulence observations for an urban area located in highly complex terrain. Using 4 years of eddy covariance measurements over the Alpine city of Innsbruck, Austria, the effects of the urban surface, orographic setting and mountain weather on energy and mass exchange are...
Numerical simulations are performed to assess the influence of horizontal and vertical model resolution on the turbulent erosion of a cold‐air pool (CAP) by foehn winds in an Alpine valley near Innsbruck, Austria. Strong wind shear in the transition zone from the CAP to the overlying foehn generates turbulence by shear‐flow instability and contribu...
In this essay, we highlight some challenges the atmospheric community is facing concerning adequate treatment of flows over mountains and their implications for numerical weather prediction (NWP), climate simulations and impact modeling. With recent increases in computing power (and hence model resolution) numerical models start to face new limitat...
We present a comprehensive analysis of four south föhn events observed during the Penetration and Interruption of Alpine Foehn (PIANO) field campaign in the Inn Valley, Austria, in the vicinity of Innsbruck. The goal is to detect and quantify processes of cold-air pool (CAP) erosion by föhn as well as processes of föhn breakdown. Despite difference...
The measures taken to contain the spread of COVID-19 in 2020 included restrictions of people's mobility and reductions in economic activities. These drastic changes in daily life, enforced through national lockdowns, led to abrupt reductions of anthropogenic CO2 emissions in urbanized areas all over the world. To examine the effect of social restri...
This study represents the first detailed analysis of multi-year near-surface turbulence observations for an urban area located in highly complex terrain. Using four years of eddy covariance measurements over the Alpine city of Innsbruck, Austria, the effects of the urban surface, orographic setting and mountain weather on energy and mass exchange a...
Processes of cold‐air pool (CAP) erosion in an Alpine valley during south foehn are investigated based on a real‐case large‐eddy simulation (LES). The event occurred during the second Intensive Observation Period (IOP 2) of the PIANO field experiment in the Inn Valley, Austria, near the city of Innsbruck. The goal is to clarify the role of advectiv...
Two urban schemes within the Joint UK Land Environment Simulator (JULES) are evaluated offline against multi-year flux observations in the densely built-up city centre of London and in suburban Swindon (UK): (i) the 1-tile slab model, used in climate simulations; (ii) the 2-tile canopy model MORUSES (Met Office–Reading Urban Surface Exchange Scheme...
Interactions between foehn and mountain-valley cold air pools (CAPs) strongly influence severe weather and air quality at the valley bottom, but have seen limited research compared to the fully established foehn phase. The Penetration and Interruption of Alpine Foehn (PIANO) campaign was conducted in the Inn Valley near Innsbruck (Austria) during f...
The Innsbruck Atmospheric Observatory (IAO) aims to investigate atmospheric chemistry, micrometeorology, and mountain meteorology in a synergistic fashion within an urban setting. A new measurement supersite has been established in order to study processes affecting the exchange of momentum, energy, trace gases, and aerosols in an Alpine urban envi...
Potential land‐climate feedbacks in subarctic regions, where rapid warming is driving forest expansion into the tundra, may be mediated by differences in transpiration of different plant functional types. Here we assess the environmental controls of overstorey transpiration and its relevance for ecosystem evapotranspiration in subarctic deciduous w...
A case‐study is presented of a south foehn emanating from the Wipp Valley, Austria, which encountered a cold‐air pool (CAP) in the Inn Valley near the city of Innsbruck. The analysis is based on data collected during the second Intensive Observation Period of the Penetration and Interruption of Alpine Foehn (PIANO) field experiment. Foehn was initi...
There is a growing need to simulate the effect of urban planning on both local climate and greenhouse gas emissions. Here, a new urban surface carbon dioxide (CO2) flux module for the Surface Urban Energy and Water Balance Scheme is described and evaluated using eddy covariance observations at two sites in Helsinki in 2012. The spatial variability...
The Surface Urban Energy and Water Balance Scheme (SUEWS) is used to investigate the impact of anthropogenic heat flux QF and irrigation on surface energy balance partitioning in a central business district of Shanghai. Diurnal profiles of QF are carefully derived based on city-specific hourly electricity consumption data, hourly traffic data, and...
Sensible heat flux (QH) is a critical driver of surface and boundary layer meteorological processes, especially in urban areas. Aerodynamic resistance methods (ARM) to model QH are promising because, in principle, all that is needed is surface temperature (T0), air temperature (TA) and an aerodynamic resistance term (rH). There are significant chal...
The snow energy balance is difficult to measure during the snowmelt period, yet critical for predictions of water yield in regions characterized by snow cover. Robust simplifications of the snowmelt energy balance can aid our understanding of water resources in a changing climate. Research to date has demonstrated that the net turbulent flux (FT) b...
Local aerodynamic roughness parameters (zero-plane displacement, z
d
, and aerodynamic roughness length, z
0
) are determined for an urban park and a suburban neighbourhood with a new morphometric parameterisation that includes vegetation. Inter-seasonal analysis at the urban park demonstrates z
d
determined with two anemometric methods is responsi...
UMEP (Urban Multi-scale Environmental Predictor), a city-based climate service tool, combines models and tools essential for climate simulations. Applications are presented to illustrate UMEP's potential in the identification of heat waves and cold waves; the impact of green infrastructure on runoff; the effects of buildings on human thermal stress...
When the urban heat island (UHI) effect coincides with a heat wave (HW), thermal stress in cities is exacerbated. Understanding the surface energy balance (SEB) responses to HWs is critical for improving predictions of the synergies between UHIs and HWs. This study evaluates observed SEB characteristics in four cities (Beijing, Łódź, London and Swi...
Climate-sensitive urban design is an increasingly important consideration for city planners and policy makers. This study demonstrates the use of a biophysical model to assess the response of urban climate to various changes, including population growth, reduced energy use, urban development and urban greening initiatives. Model inputs are intentio...
The city based climate service tool UMEP (Urban Multi-scale Environmental Predictor) is a coupled modelling system that combines models essential for urban climate processes and is developed as an extensive QGIS plugin. An application is presented to illustrate its potential, speci�cally of the identi�cation of heat waves and cold waves in cities....
Representative precipitation data sets are very difficult to obtain due to the inherent spatial and temporal variability of rainfall. Gridded rainfall products exist at various scales, but temporal resolution is coarse (daily or, at best, a few hours). This study demonstrates the impact of low temporal resolution precipitation forcing data (PFD) on...
Often the meteorological forcing data required for urban hydrological models are unavailable at the required temporal resolution or for the desired period. Although reanalysis data can provide this information, the spatial resolution is often coarse relative to cities, so downscaling is required prior to use as realistic forcing. In this study, WAT...
Knowledge of turbulent exchange in complex environments is relevant to a wide range of hydro-meteorological applications. Observations are required to improve understanding and inform model parameterisations but the very nature of complex environments presents challenges for measurements. Scintillometry offers several advantages as a technique for...
Spatially-integrated measurements of the surface energy balance (SEB) are needed in urban areas to evaluate urban climate models and satellite observations. Scintillometers allow observations of sensible heat flux (QH) over much larger areas than techniques such as eddy covariance (EC), however methods are needed to partition between remaining unme...
The Surface Urban Energy and Water Balance Scheme (SUEWS) is evaluated at two locations in the UK: a dense urban site in the centre of London and a residential suburban site in Swindon. Eddy covariance observations of the turbulent fluxes are used to assess model performance over a two-year period (2011−2013). The distinct characteristics of the si...
Manual for SUEWS (Surface Urban Energy and Water balance Scheme) V2016a
http://urban-climate.net/umep/SUEWS
Cosmic-ray soil moisture sensors have the advantage of a large measurement footprint (approximately 700m in diameter) and are able to operate continuously to provide area-averaged near-surface (top 10-20cm) volumetric soil moisture content at the field scale. This paper presents the application of this technique at four sites in southern England ov...
Field measurements of soil water content have many potential uses beyond merely monitoring changes in water storage of a soil profile. The neutron probe method has been applied widely to measure the effect of differences in evaporation losses from different vegetation on soil water balances. A number of key studies of unsaturated zone water balance...
In the London case study the social and biophysical aspects of heat-waves are considered. The aim is to study the key controls on heat-waves in Greater London and the impact of governance to individual behaviours including support networks in the context of heat-wave resilience in the city. To achieve this two groups have collaborated: the social s...
Scintillometry, a form of ground-based remote sensing, provides the
capability to estimate surface heat fluxes over scales of a few hundred
metres to kilometres. Measurements are spatial averages, making this
technique particularly valuable over areas with moderate heterogeneity such
as mixed agricultural or urban environments. In this study, we pr...
A millimetre-wave scintillometer was paired with an infrared scintillometer, enabling estimation of large-area evapotranspiration across northern Swindon, a suburban area in the UK. Both sensible and latent heat fluxes can be obtained using this "two-wavelength" technique, as it is able to provide both temperature and humidity structure parameters,...
Anthropogenic and biogenic controls on the surface-atmosphere exchange of CO2 are explored for three different environments. Similarities are seen between suburban and woodland sites during summer, when photosynthesis and respiration determine the diurnal pattern of the CO2 flux. In winter, emissions from human activities dominate urban and suburba...
A millimetre-wave scintillometer was paired with an infrared
scintillometer enabling estimation of large-area evaporation across
northern Swindon, a suburban area in the UK. Both sensible and latent
heat fluxes can be obtained using this technique, as it is able to
provide both temperature and humidity structure parameters, offering
a major advanta...
Scintillometry, a form of ground-based remote sensing, provides the capability to estimate surface
heat fluxes over scales of a few hundred metres to kilometres. Measurements are spatial averages,
making this technique particularly valuable over areas with moderate heterogeneity such as mixed
agricultural or urban environments. In this study, we pr...
During the winter of 2013/14, much of the UK experienced repeated intense rainfall events and flooding. This had a considerable impact on property and transport infrastructure. A key question is whether the burning of fossil fuels is changing the frequency of extremes, and if so to what extent. We assess the scale of the winter flooding before revi...
During the winter of 2013/14, much of the UK experienced repeated intense rainfall events and flooding. This had a considerable impact on property and transport infrastructure. A key question is whether the burning of fossil fuels is changing the frequency of extremes, and if so to what extent. We assess the scale of the winter flooding before revi...
Sensible heat fluxes (QH ) are determined using scintillometry and eddy covariance over a suburban area. Two large-aperture scintillometers provide spatially integrated fluxes across path lengths of 2.8 and 5.5 km over Swindon, UK. The shorter scintillometer path spans newly built residential areas and has an approximate source area of 2-4 {km}2 ,...
Simultaneous scintillometer measurements at multiple wavelengths (pairing visible or infrared with millimetre or radio waves) have the potential to provide estimates of path-averaged surface fluxes of sensible and latent heat. Traditionally, the equations to deduce fluxes from measurements of the refractive index structure parameter at the two wave...
Eddy covariance measurements of the turbulent sensible heat, latent heat and carbon dioxide fluxes for 12 months (2011-2012) are reported for the first time for a suburban area in the UK. The results from Swindon are comparable to suburban studies of similar surface cover elsewhere but reveal large seasonal variability. Energy partitioning favours...
Extrapolating biosphere-atmosphere CO2 flux observations to larger scales in space, part of the so-called “upscaling” problem, is a central challenge for surface-atmosphere exchange research. Upscaling CO2 flux in tundra is complicated by the pronounced spatial variability of vegetation cover. We demonstrate that a simple model based on chamber obs...
Unravelling the role of structural and environmental drivers of gross primary productivity (GPP) and ecosystem respiration (R
eco) in highly heterogeneous tundra is a major challenge for the upscaling of chamber-based CO2 fluxes in Arctic landscapes. In a mountain birch woodland-mire ecotone, we investigated the role of LAI (and NDVI), environmenta...
a b s t r a c t Scintillometry is an established technique for determining large areal average sensible heat fluxes. The scintillometer measurement is related to sensible heat flux via Monin–Obukhov similarity theory, which was developed for ideal homogeneous land surfaces. In this study it is shown that judicious application of scintillometry over...
Airflow along rivers might provide a key mechanism for ventilation in cities: important for air quality and thermal comfort. Airflow varies in space and time in the vicinity of rivers. Consequently, there is limited utility in point measurements. Ground-based remote sensing offers the opportunity to study 3D airflow in locations which are difficult...
Eddy covariance measurements of the turbulent sensible heat, latent heat
and carbon dioxide flux for twelve months (2011-2012) are reported for
the first time for a suburban area in the UK. The results from Swindon
are compatible with suburban studies of similar surface cover elsewhere
but reveal large seasonal variability. Energy partitioning favo...
The effects of a non-uniform wind field along the path of a scintillometer are investigated. Theoretical spectra are calculated for a range of scenarios where the crosswind varies in space or time and compared to the 'ideal' spectrum based on a constant uniform crosswind. It is verified that the refractive-index structure parameter relation with th...
This study presents the initial results of a comparison between turbulence
measurements in London, UK, using three models of scintillometers at different
scales. Within the densely built-up area of central London a Large Aperture
Scintillometer (LAS) manufactured by Kipp and Zonen (LAS 150) was aligned along
a 4.1 km path with a mean beam heigh...