Endurance.Net Ridecamp Archives

Title: “I maintain there is much more wonder in science than in pseudoscience

There are many factors that relate to the head load in a horse, or human for that matter. First is the air temp - which is what is reported as temp. That's the temp in the shade. The next is the humidity as reported as relative humidity or maybe dew point temp. Normally unless dryer or wetter air moves in the dew point temp is pretty constant and the relative humidity varies with temp. When the dew point temp = the air temp the humidity is 100%. The relative humidity drops from that by about 5% for every rise of 1 deg C (1.8 deg F) for relative humidity above 50% (it gets more complicated below that). The air temp cannot drop below the dew point since water vapor is a "greenhouse gas" and will release heat energy into the air to keep it at the dew point. The humidity does not impart heat (except as noted above), however, it impacts the efficiency of evaporative cooling. The cooling efficiency is in direct proportion to the difference between the air temp and dew point temp. When they are equal the air is saturated and there is no evaporative cooling.

The third source is radiant energy - direct sunlight. The temp felt in the sun is higher than that felt in the shade (air temp). Don't believe it, you could fry an egg on the pavement in the sun in Texas on a sunny day but not on pavement in the shade. That difference is from the radiant heating of the pavement. And yes because the sun is more overhead in the Souther tier of states - the radiant heat energy load is much greater. This becomes a real issue when riding in the sun. Dark colors absorb more radiant energy than light colors so dark horses have an additional heat load from radiant energy in the sun.

Truman

carolyn@xxxxxxxxxxxxxxxxxxxx wrote:

The biggest problem I had when I moved south (from Massachusetts to southeast Texas) was getting my horses used to the strength of the sun, not necessarily the heat or humidity as we had both in Massachusetts. But the intensity of the sun was something I had never seen before.  It took my horses an entire year (spring/summer/fall/winter) to get used to the heat.  4 of them are great in the heat, they never liked the cold anyway and required mountains of blankets.  I have one older horse who was born and raised in Maine, and on the hotest of days does sweat alot. 

Carolyn Burgess
Newton, Texas

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“I maintain there is much more wonder in science than in pseudoscience. And in addition, to whatever measure this term has any meaning, science has the additional virtue, and it is not an inconsiderable one, of being true.” Carl Sagan