These limits are what limit you when there are no obstacles to think about.
Don't have the exact figures to hand but if I remember correctly for a twin like the B737,
With no obstacles you still have to acheive
Departure Climb Gradients;
1st segment - positive
2nd segment - 2.4% one engine inop or 5.2% all engines
3rd segment - 1.2% one engine inop
4th segment - 1.2% one engine inop or 4.0% all engines
Landing Climb Gradients;
1500ft above the aerodrome, a positive gradient
Baulked Landing Climb - 3.2% in the landing config with all engines operating
Approach Climb - one engine inoip, gear up - 2.1%
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These are often called the "Weight, Altitude Temperature" (WAT) limits. As altitude and temperature increase with no other limitations you will have to reduce weight to acheive these gradients.
If you have obstacles, you may have to acheive higher gradients. Similarly, the mised approach from an instrument approach procedure may also require a higher gradient - 2.5% or more.
Regards,
DFC