Improved climate-readiness of

intensive livestock management

through use of a Heat Load Index

as an indicator of heat stress

Presented by

Andrew Wiebe

Principle Meteorology & Forecasting

KATESTONE

National Climate Change Adaptation Research Facility conference 2013

17 May 2013

• Heat wave verses heat load

• Heat management solution for the Australian cattle

feedlot industry

• Review of 2013 summer event

• Application to management of human heat stress

• Questions

Outline

Background

• The Australian beef cattle industry has an estimated economic worth of $7.9 billion per year

• Australia’s largest agricultural exporter

• Health and well being of cattle has significant economic and moral implications

• Heat stress can lead to reduced production and even cattle death

• MLA has invested significant R&D over more then 10 years to address the issue

• Katestone developed first trial forecasts in 2001

• Cattle deaths reduced since introduction of system

Managing Cattle Heat Load

http://www.weeklytimesnow.com.au/article/2012/04/05/466081_latest-news.html

http://www.ddt.com.au/product-range/view/33/17/shade-products/cattle-shade

http://www.feedlots.com.au/index.php?option=com_content&view=article&id=89&Itemi

d=118

HEAT LOAD EVENT

When a heat wave is not a

Heat Wave

• Generally uncomfortably hot

for the population and may

adversely affect human

health

• Period of unseasonable or

exceptionally hot weather

• Number of consecutive days

where daily maximum

temperature reaches some

threshold

• Places too much emphasis

on daily maximum

temperature

• Misses important aspects of

the environment, such as

wind speed, humidity and

radiant energy absorption and

dissipation

Cattle Heat Load (HLI)

• A high ongoing minimum and maximum ambient temperature

• A high ongoing relative humidity

• High solar radiation level

• Minimal air movement

• A sudden change to adverse conditions

• “A combination of some or all of these conditions over a period of 2

to 5 days that leads to an excessive heat load event and can result

in cattle death”

Gaughan et al., 2008. A new heat load index for feedlot cattle. Journal of Animal Science, vol.

86 no. 1 226-234

HLI equation

if BGT < 25°C :

HLI = 10.66 + (0.28 * RH) + (1.3 * BGT )– WS

if BGT > 25°C :

HLI = 8.62 + (0.38 * RH) + (1.55 * BGT) – (0.5 * WS) + e(2.4 - WS)

Where:

BGT = Black globe temperature

T = temperature (°C)

SR = solar radiation (W/m²)

RH = relative humidity (decimal form)

WS = wind speed (m/s)

8

Accumulated Heat Load

• The accumulation and dissipation of heat load is defined by

Accumulated Heat Load Units (AHLU).

• Different levels of AHLU have been assigned to signify different

cattle types and conditions ranging from 80 to 95, where AHLU 80

cattle will start accumulating heat load when the HLI is above 80 and

so on for all cattle types.

• All cattle types will start dissipating heat load when the HLI drops

below 77

• HLI values between 77 and the accumulation level (i.e. 80) are

thermal neutral zone no accumulation or dissipation occurs.

AHLU Risk Level

AHLU Heat stress Cattle indicator

0-20 Low risk No stress or panting

score 1

20-50 Medium risk Panting score 1-2

50-100 High risk Panting score 2-4

Over 100 Extreme risk Panting score 4

“The Angry Summer”

• “The summer of 2012/2013

was Australia’s hottest

summer since records

began in 1910”

• January 7 2013 hottest ever

area-averaged Australian

maximum temperature,

40.3°C

• 44 weather stations had all-

time maximum temperatures

• January 2 to 8 and January

11 2013 area-averaged

maximum temperature

exceeded 39°C

High daily HLI / Low

Accumulated Heat Load • January 7 2013

• Area-averaged maximum

daily HLI 81.5

• AHLU low to Moderate

• Low moisture, 5 -7% RH

• Overnight recovery

• January 2 – 8 Area-

averaged maximum daily

HLI of 80

Heat Load Event

• January 12 to February

2 Heat Load event

• Area-averaged

maximum HLI 83.5

• Maximum January 12

HLI 87.5

• Followed by January 18

HLI 85.6

• AHLU High to Extreme

• Overnight recovery

limited

Heat Load Event •Mean Max Temp: 30°C

•Mean Max HLI: 79

•Nov 2012-March2013

•230 BOM AWS

Heat Load Event •Mean Min Temp: 18°C

•Mean Min HLI: 53

•Nov 2012-March 2013

•230 BOM AWS

“Dome of Heat”

• January 11 1600 2013

• Hot dry air mass

• Gusty winds

Minimal Heat Load

End of Heatwave

• January 12 1600 2013

• Hot dry air mass

dissipates

• Influx of moist tropical

air mass

• Pockets of still air near

surface

Heat Load

Managing Human Heat Load

Many methods exist:

• Apparent temperature Steadman, 1984

– Complex version uses wind speed and absorbed radiation

• Heat Index Rothfusz, 1990

• HUMIDEX Masterson & Richardson, 1979

• WBGT Yaglou & Minard, 1984

• Simplified WBGT ABOM, ACSM, 1984

• Environmental Stress Index (ESI) Moran et al., 2001

• Excess Heat Factor Nair & Fawcett 2013

How to apply them under varying conditions, locations and activities?

Wet Bulb Globe Temperature

• ISO Standard 7243 WBGT hot environments

• Requires natural wet bulb temperature and black globe temperature

– Not standard AWS sensors

– Can be derived

– No long term datasets

• BOM approximation (simplified WBGT)

– Assumes moderately high solar radiation levels

– Assumes light winds

– Tends to overestimate heat stress

WBGT = 0.567 x Ta + 0.393 x e + 3.94

Where : Ta = Air temperature °C

e = vapour pressure hPa

Heatwave ≠ Heat Load • Definitions do not

account for overnight

recovery

• No acclimatisation

factors

• Neglects cooling effects

of wind

• Neglects importance of

evaporative cooling

• Concentrates on

sensible heat load and

accumulation

• Ignores latent heat load

and accumulation

Simplified WBGT BOM 2013

Implications

Obviously different physiology and behaviours but are the meteorological

variables and climatic conditions similar?

Do current heat stress indicators for human health miss the point?

The Australian feedlot industry are ready to tackle a changing climate but are

we?

Thank You

Thanks to Meat and Livestock

Australia for continued support

and the rest of the Katestone

team.

Please e-mail any questions to

andrew.wiebe@katestone.com.au

Katestone

PO Box 2217

Milton, QLD, 4064

References • John Nairn and Robert Fawcett (2013), “Defining heatwaves: heatwave defined as a heat impact event

servicing all community and business sectors in Australia” The Centre for Australian Weather and Climate

research - a partnership between CSIRO and the Bureau of Meteorology CAWCR Technical Report

No. 060

• John P. Dunne, Ronald J. Stouffer, Jasmin G. John (2013). “Reductions in labour capacity from heat

stress under climate warming”. Nature Climate Change, DOI: 10.0138/NCLIMATE1827

• E.M. Fischer, R. Knutti (2012). “Robust projections of combined humidity and temperature extremes”.

Nature Climate Change, DOI: 10.1038/NCLIMATE1682

• Ken Parsons (2006). “Heat Stress Standard ISO 7243 and its Global Application”. Industrial Health 2006,

44, 368-379

• G.S. Stipanuk (1973). "Algorithms for generating a Skew-T, Log P diagram and computing selected

meteorological quantities.” Atmospheric Sciences Laboratory, U.S. Army Electronics Command, White

Sands Missile Range, New Mexico

• C.H. Hunter, C.O. Minyard (1999). “Estimating wet bulb globe temperature using standard meteorological

measurements”. US Department of Energy, Office of Scientific and Technical Information, WSRC-MS-99-

00757, 2.7

• V.E. Dimiceli, S.F. Piltz, S.A. Amburn (2011). “Estimation of Black Globe Temperature for Calculation of

the Wet Bulb Globe Temperature Index”. Proceedings of the World Congress on Engineering and

Computer Science 2011, Vol 2

• Sports Medicine Australia (2007), “Hot Weather Guidelines for sporting clubs and the physically active”

Accessed 04/06/13 at sma.org.au