UNSTABLE, DRI and Water Cycling Ronald Stewart McGill University

Specific Objectives of Presentation To briefly review DRI and some of its science Comment on interactions with UNSTABLE

Prairie Drought

CONCERNS There are many concerns associated with drought but many of these can be summarized under two broad categories Will there be a drought? decadel seasonal ‘now’ How do we best prepare for and cope with drought? many perspectives

The frequency and severity of droughts are likely to increase in southern Canada Return Period (years) Length of Dry Spell (days) Central North America Today ~2070 Gregory et al., 1997

Let’s first of all understand how drought develops, is sustained, and ends and how it is structured

WATER AND ENERGY CYCLING Drought is an aberration in the Water and energy cycle

Extreme Drought Extreme Wet

DRI Objective To better understand and contribute to the better prediction of drought … Focus mainly but not exclusively on the recent Prairie drought

New developments in using satellite measurements of stable isotopes of water Source: Worden, J. et al. Importance of rain evaporation and continental convection in the tropical water cycle. Nature 445,

Uncertainties in the hydrological cycle Moisture transport and circulation within the atmosphere is an integral part of the hydrological cycle, but is not well quantified: –Atmospheric moisture can come from both oceanic and local evaporative sources, but the relative contribution of each to the overall moisture for a given region is not easily determined –Measuring stable isotope ratios in water vapour may help to reveal and better indicate the relative sources of moisture

Measuring stable isotopes of tropospheric water vapour from space Simultaneous profiles of HDO and H 2 O vapour are obtained using the Tropospheric Emission Spectrometer (TES) aboard the NASA Aura satellite From this, the first comprehensive map of the global distribution of deuterium (shown as the ratio δD) in water vapour is obtained

Next plot Unit: parts per thousand by volume Oct 04 – March 05 IR emissions 5 km by 8 km footprint

DEUTERIUM IN WATER VAPOUR hPa layer Tropospheric Emission Spectrometer: Aqua satellite

CLOUD AMOUNT

Characterizing precipitation at Calgary, AB Seasonal total precipitation:

Days with precipitation Calgary The fraction of days receiving any amount of precipitation: Climatology ( ): 40% Drought ( ): 46% Sub-Drought ( ): 43%

Climatology: Low precipitation events (≤ 10 mm) account for 52% of total precipitation Daily Total Precipitation Amount Distribution

Climatology Low precipitation events: 52% of total Drought Low precipitation events: 58% of total Sub-drought Low precipitation events: 60% of total

Climatology Low precipitation events: 52% of total Sub-drought Low precipitation events: 60% of total Daily Precipitation Amounts Calgary Low precipitation event: < 10 mm

What factors led to the ≤10 mm events? Possibilities include Loss due to evaporation/sublimation Short-lived weather systems Change in character of clouds Fast moving weather systems …

RADAR PROFILES 1 June 2002: Calgary Scattered stratiform rain early Late in the day there is evidence of water aloft (~5 km) This appears to be high-level moisture as a precursor to the rainy pattern on the following day

VIRGA Courtesy of Barrie Bonsal

VEGETATION July 11-20, 2002 NDVI NDVI: Normalized Difference Vegetation Index Healthy vegetation

SOME ATMOSPHERIC WATER CYCLING ISSUES Water Cycle Issues include: Is precipitation being formed aloft? Will precipitation reach the ground? What is the water vapour source for the precipitation? How is the water vapour (re-)distributed in the vertical and horizontal? What is the diurnal cycle of the precipitation? Where does the precipitation occur? … Contributing factors include: Type and organization of precipitating system Cloud base height Drop sizes Surface...

UNSTABLE Sub-objectives include … to better understand, resolve, and quantify: spatial extent, depth and temporal evolution of water vapour in the atmospheric boundary layer Mesoscale effects on thunderstorms effects of variable surface …

DRI and UNSTABLE DRI diverse research expertise (~ 30) datasets (atmosphere, surface …) analysis tools (DAI …) … UNSTABLE aspects linked with water cycling focused activity observational and model products …

CONCLUDING REMARKS DRI is concerned with: the science of water cycling UNSTABLE is concerned with: overturning of the atmosphere DRI and UNSTABLE can benefit from collaboration

And … thank you for your attention